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Index Chapter Name Page 1) C# interview Questions and Answers. 4 1.1) Advance C# interview Questions 2) General Questions 17 2.1 ) General Questions 2.2 ) Methods and Property 2.3) Assembly Questions 2.4) XML Documentation Question 2.5) Debugging and Testing 3) ADO.net and Database Question 26 4) C#, DOT NET, XML, IIS Interview Questions 28 4.1 ) Framework. 4.2 ) COM 4.3 ) OOPS 4.4 ) C# Language Features 4.5 ) Access Specifier 4.6 ) Constructor / Destructor 4.7 ) ADO.net 4.8 ) ASP.net 4.8.1) Session. 4.8.2) Security. 4.8.3) Web Servcing & Remoting 4.9 ) XML 4.10 ) IIS 4.11 ) Controls 4.12 ) Programming 5) Dot NET. 120 5.1 ) Dot NET 5.2 ) Basic Technology. 5.3 ) Assemblies 5.4 ) Application Domain 5.5 ) Garbeg collection 5.6 ) Serialization


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5.7 ) Attribute 5.8 ) Code Access Security. 5.9 ) Interimediate Language (IL) 5.10 ) Implications for COM. 5.11 ) Miscellaneous 5.12 ) Class Library 5.12.1) File I/ O 5.12.2 ) Text Processing 5.12.3 ) Internet. 5.12.4) XML 5.12.5) Threading 5.12.6) Tracing. 6) C# FAQ's 151 6.1 ) Introduction 6.2 ) Basic Datatype. 6.3 ) Classes & Structs. 6.4 ) Exceptions 6.5 ) Runtime type information. 6.7 ) Advantage features. 6.8 ) Miscellaneous. 7) Interview Questions for Dot NET Forms. 161 8) Interview Questions for Dot NET Remoting 164 9) Interview Questions for ASP .NET 167 10 ) ASP.NET ,C#, VB.NET and COM etc�.Full of microsoft Technology 173 11 ) .NET Framework FAQ's 204 12 ) C# and VB.NET 285 13) COM & COM + 307 14 ) Remoting FAQ's 311 15 ) WinForms FAQ 316


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C# Interview Questions and Answers Q 1. What�s the implicit name of the parameter that gets passed into the class�

set method?

Ans: - Value and its data type depend on whatever variable we�re changing.

Q 2. How do you inherit from a class in C#?

Ans: - Place a colon and then the name of the base class. Notice that it�s double colon in C++.

Q 3. Does C# support multiple inheritances?

Ans: - No, use interfaces instead.

Q 4. When you inherit a protected class-level variable, who is it available to?

Ans: - Classes in the same namespace.

Q 5. Are private class-level variables inherited?

Ans: - Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.

Q 6. Describe the accessibility modifier protected internal?

Ans: - It�s available to derived classes and classes within the same Assembly (and naturally from the base class it�s declared in).

Q 7. C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?

Ans: - Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there�s no implementation in it.

Q 8. What�s the top .NET class that everything is derived from?

Ans: - System. Object.


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Q 9. How�s method overriding different from overloading?

Ans: - When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.

Q 10. What does the keyword virtual mean in the method definition?

Ans: - The method can be over-ridden.

Q 11. Can you declare the override method static while the original method is non-static?

Ans: - No, you can�t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

Q 12. Can you override private virtual methods?

Ans: - No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.

Q 13. Can you prevent your class from being inherited and becoming a base class for some other classes?

Ans: - Yes, that�s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class Whatever Base Class Name. It�s the same concept as final class in Java.

Q 14. Can you allow class to be inherited, but prevent the method from being over-ridden?

Ans: - Yes, just leave the class public and make the method sealed.

Q 16. What�s an abstract class?

Ans: - A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it�s a blueprint for a class without any implementation.


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Q 17. When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?

Ans: - When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.

Q 18. What�s an interface class?

Ans: - It�s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

Q 19. Why can�t you specify the accessibility modifier for methods inside the interface?

Ans: - They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, its public by default.

Q 20 Can you inherit multiple interfaces?

Ans: - Yes, why not.

Q 21. And if they have conflicting method names?

Ans: - It�s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you�re okay.

Q 22. What�s the difference between an interface and abstract class?

Ans: - In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.

Q 23. How can you overload a method?

Ans: - Different parameter data types, different number of parameters, different order of parameters.


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Q 24. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?

Ans: - Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

Q 25. What�s the difference between Systems? String and System.StringBuilder classes?

Ans: - System. String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

Q 26. What�s the advantage of using System.Text.StringBuilder over System String?

Ans: - String Builder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it�s being operated on, a new instance is created.

Q 27. Can you store multiple data types in System? Array?

Ans:- No.

Q 28. What�s the difference between the System.Array.CopyTo () and System.Array.Clone ()?

Ans: - The first one performs a deep copy of the array, the second one is shallow.

Q 29. How can you sort the elements of the array in descending order?

Ans: - By calling Sort () and then Reverse () methods.

Q 30. What�s the .NET data type that allows the retrieval of data by a unique key?

Ans: - Hash Table.

Q 31. What�s class Sorted List underneath?

Ans: - A sorted Hash Table.


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Q 32. Will finally block get executed if the exception had not occurred?

Ans: - Yes.

Q 33. What�s the C# equivalent of C++ catch (�), which was a catch-all statement for any possible exception?

Ans: - A catch block that catches the exception of type System. Exception. You can also omit the parameter data type in this case and just write catch {}.

Q 34. Can multiple catch blocks be executed?

Ans: - No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

Q 35. Why is it a bad idea to throw your own exceptions?

Ans: - Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.

Q 36. What�s a delegate?

Ans:- A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.

Q 37. What�s a multicast delegate?

Ans: - It�s a delegate that points to and eventually fires off several methods.

Q 38 How�s the DLL Hell problem solved in .NET?

Ans: - Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.

Q 39. What are the ways to deploy an assembly?

Ans: - An MSI installer, a CAB archive, and XCOPY command.


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Q 40. What�s a satellite assembly?

Ans: - When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.

Q 41. What namespaces are necessary to create a localized application?

Ans: - System. Globalization, System. Resources.

Q 42. What�s the difference between // comments, /* */ comments and /// comments?

Ans: - Single-line, multi-line and XML documentation comments.

Q 43 How do you generate documentation from the C# file commented properly with a command-line compiler?

Ans: - Compile it with a /doc switch.

Q 44. What�s the difference between <c> and <code> XML documentation tag?

Ans: - Single line code example and multiple-line code example.

Q 45. Is XML case-sensitive?

Ans: - Yes, so <Student> and <student> are different elements.

Q 46. What debugging tools come with the .NET SDK?

Ans: - CorDBG � command-line debugger, and DbgCLR � graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

Q 47. What does the window show in the debugger?

Ans: - It points to the object that�s pointed to by this reference. Object�s instance data is shown.


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Q 48. What does assert () do?

Ans: - In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

Q 49. What�s the difference between the Debug class and Trace class?

Ans: - Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.

Q 50. Why are there five tracing levels in System.Diagnostics.TraceSwitcher?

Ans: - The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from none to Verbose, allowing fine-tuning the tracing activities.

Q 51. Where is the output of TextWriterTraceListener redirected?

Ans: - To the Console or a text file depending on the parameter passed to the constructor.

Q 52. How do you debug an ASP.NET Web application?

Ans: - Attach the aspnet_wp.exe process to the DbgClr debugger.

Q 53. What are three test cases you should go through in unit testing?

Ans: - Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).

Q 54. Can you change the value of a variable while debugging a C# application?

Ans: - Yes, if you are debugging via Visual Studio.NET, just go to immediate window.

Q 55. Explain the three services model (three-tier application)?

Ans: - Presentation (UI), business (logic and underlying code) and data (from storage or other sources).


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Q 56. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Ans: - SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it�s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.

Q 57. What�s the role of the Data Reader class in ADO.NET connections?

Ans: - It returns a read-only dataset from the data source when the command is executed.

Q 58. What is the wildcard character in SQL? Let�s say you want to query database with LIKE for all employees whose name starts with La.

Ans: - The wildcard character is %, the proper query with LIKE would involve �La%�.

Q 59. Explain ACID rule of thumb for transactions?

Ans: - Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no �in-between� case where something has been updated and something hasn�t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).

Q 60. What connections does Microsoft SQL Server support?

Ans: - Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).

Q 61. Which one is trusted and which one is untrusted?

Ans: - Windows Authentication is trusted because the username and password are checked with the Active Directory; the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.

Q 62. Why would you use untrusted verificaion?

Ans: - Web Services might use it, as well as non-Windows applications.


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Q 63. What does the parameter Initial Catalog define inside Connection String?

Ans: - The database name to connect to.

Q 64. What�s the data provider name to connect to Access database?

Ans: - Microsoft. Access.

Q 65. What does dispose method do with the connection object?

Ans: - Deletes it from the memory.

Q 66. What is a pre-requisite for connection pooling?

Ans: - Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.


Ans: - Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.

Advanced C# interview questions . Q 68. Can you store multiple data types in System? Array?

Ans: - No.

Q 69. What�s the difference between the System.Array.CopyTo () and System.Array.Clone ()?

Ans: - The first one performs a deep copy of the array, the second one is shallow.




Ans: - Yes.


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Ans: - No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.


Ans: - Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.


Ans: - A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.



Q 78. How�s the DLL Hell problem solved in .NET?




Q 80. What�s a satellite assembly?



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Q 81. What namespaces are necessary to create a localized application?

Ans: - System. Globalization, System.Resources.

Q 82. What�s the difference between // comments, /* */ comments and /// comments?

Ans: - Single-line, multi-line and XML documentation comments.

Q 83. How do you generate documentation from the C# file commented properly with a command-line compiler?

Ans: - Compile it with a /doc switch.

Q 84. What�s the difference between <c> and <code> XML documentation tag?



Ans: - Yes, so <Student> and <student> are different elements.

Q 86. What debugging tools come with the .NET SDK?

Ans: - CorDBG � command-line debugger, and DbgCLR � graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.

Q 87. What does the window show in the debugger?


Q 88. What does assert () do?

Ans: - In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.

Q 89. What�s the difference between the Debug class and Trace class? Documentation looks the same?

Ans: - Use Debug class for debug builds, use Trace class for both debug and release builds.


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Ans: - The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from none to Verbose, allowing fine-tuning the tracing activities.

Q 91. Where is the output of TextWriterTraceListener redirected?

Ans: - To the Console or a text file depending on the parameter passed to the constructor.




Ans: - Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).


Ans: - Yes, if you are debugging via Visual Studio.NET, just go to immediate window.

Q 95. Explain the three services model (three-tier application)?


Q 96. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Ans :- SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it�s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.


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Q 97. What�s the role of the Data Reader class in ADO.NET connections?


Q 98. What is the wildcard character in SQL? Let�s say you want to query database with LIKE for all employees whose name starts with La?

Ans: - The wildcard character is %, the proper query with LIKE would involve �La%�.

Q 99. Explain ACID rule of thumb for transactions?

Ans: - Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no �in-between� case where something has been updated and something hasn�t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).


Ans: - Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).


Ans :- Windows Authentication is trusted because the username and password are checked with the Active Directory; the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.



Q 103. What does the parameter Initial Catalog define inside Connection String?



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Q 104. What�s the data provider name to connect to Access database?

Ans: - Microsoft. Access.

Q 105. What does dispose method do with the connection object?


General Questions Q 106. Does C# support multiple-inheritance?

Ans: - No, use interfaces instead.

Q 107. When you inherit a protected class-level variable, who is it available to?

Ans :- Classes in the same namespace.

Q 108. Are private class-level variables inherited?

Ans :- Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.

Q 109. Describe the accessibility modifier �protected internal�.

Ans :- It is available to derived classes and classes within the same Assembly (and naturally from the base class it�s declared in). To do: Confirm the �within the same assembly� portion.

Q 110. C# provides a default class constructor for me. I decide to write a constructor that takes a string as a parameter, but want to keep the constructor that has no parameter. How many constructors should I write?

Ans :- Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there�s no implementation in it.


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Q 111. What�s the top .NET class that everything is derived from?

Ans :- System. Object.

Q 112. What�s the difference between Systems? String and System.StringBuilder classes?

Ans :- System. String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.

Q 113. What�s the advantage of using System.Text.StringBuilder over System. String?

Ans :- String Builder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time it�s being operated on, a new instance is created.

Q 114. Can you store multiple data types in System. Array?

Ans :- No.

Q 115 what�s the difference between the System.Array.CopyTo () and System.Array.Clone ()?

Ans:-The first one performs a deep copy of the array, the second one is shallow.

1. To do: improve the answer.

Q 116. . How can you sort the elements of the array in descending order?


Q 117. What�s the .NET class that allows the retrieval of a data element using a unique key?

Ans :- Hash Table.


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Q 118 Will the finally block get executed if an exception has not occurred?

Ans: - Yes.




Ans: - No. Once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.

Q 121. Explain the three services model commonly know as a three-tier application?


Q 122. What is the role of the Data Reader class in ADO.NET connections?


Class Questions Q 123. How do you inherit from a class in C#?

Ans: - Place a colon and then the name of the base class.

Q 124. Can you prevent your class from being inherited by another class?


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Ans: - Yes. The keyword �sealed� will prevent the class from being inherited.

Q 125. Can you allow a class to be inherited, but prevent the method from being over-ridden?

Ans: - Yes. Just leave the class public and make the method sealed.

Q 126. What�s an abstract class?

Ans: - A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.

Q 127. When do you absolutely have to declare a class as abstract?

Ans :- 1. When at least one of the methods in the class is abstract.

2. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden.

Q 128. What�s an interface class?

Ans: - It�s an abstract class with public abstract methods all of which must be implemented in the inherited classes.

Q 129. Why can�t you specify the accessibility modifier for methods inside the interface?

Ans: - They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, its public by default.

Q130. Can you inherit multiple interfaces?

Ans: - Yes, why not.


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Q 131. And if they have conflicting method names?

Ans: - It�s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you�re okay.

Q 132. What�s the difference between an interface and abstract class?

Ans: - In an interface class, all methods must be abstract. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed, which is ok in an abstract class.

Q 133. What is the difference between a Struct and a Class?

Ans :- Structs are value-type variables and are thus saved on the stack -> additional overhead but faster retrieval. Another difference is that structs CANNOT inherit. (Questions courtesy of Eyal)

Method and Property Questions Q 134. What�s the implicit name of the parameter that gets passed into the

set method/property of a class?

Ans: - The data type of the value parameter is defined by whatever data type the property is declared as.

Q 135. What does the keyword �virtual� declare for a method or property?

Ans: - The method or property can be overridden.

Q 136. How is method overriding different from method overloading?


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Ans: - When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.

Q 137. Can you declare an override method to be static if the original method is non-static?

Ans: - No. The signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.

Q 138. Can you override private virtual methods?

Ans: - No. Private methods are not accessible outside the class.

Original answer: No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access

To do: Can a private method even be declared a virtual?

Q 139.. What are the different ways a method can be overloaded?

Ans: - parameter data types, different number of parameters, different order of parameters.

Q 140. If a base class has a number of overloaded constructors, and an inherited class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?

Ans: - Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.


Ans: - Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new


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Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.


Ans :- A delegate object encapsulates a reference to a method.



Assembly Questions Q 153. How is the DLL Hell problem solved in .NET?




Q 155. What is a satellite assembly?


Q 156.. What namespaces are necessary to create a localized application? Ans: - System. Globalization and System.Resources.

XML Documentation Questions Q 157 what�s the difference between // comments, /* */ comments and /// comments?

Ans :- Single-line comments, multi-line comments, and XML documentation comments.


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Ans: - Compile it with the /doc switch.

Q 159.What the difference is between and XML documentation tag?



Ans :- Yes.

Debugging and Testing Questions Q 161. What debugging tools come with the .NET SDK?

Ans :-

1. CorDBG � command-line debugger. To use CorDbg, you must compile the original C# file using the /debug switch.

2. DbgCLR � graphic debugger. Visual Studio .NET uses the DbgCLR.

Q 162. What does the �This� window show in the debugger?


Q 163.. What does assert () method do?

Ans :-In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.


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Q 164. What�s the difference between the Debug class and Trace class?

Ans:-Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.


Ans:-The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from none to Verbose, allowing you to fine-tune the tracing activities.

Q 166 where is the output of TextWriterTraceListener redirected?

Ans :-To the Console or a text file depending on the parameter passed to the constructor.




1. Positive test cases (correct data, correct output).

2. Negative test cases (broken or missing data, proper handling).

3. Exception test cases (exceptions are thrown and caught properly).


Ans: - Yes. If you are debugging via Visual Studio.NET, just go to Immediate window.


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ADO.NET and Database Questions Q 170. What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET?

Ans: - SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix. OLE-DB.NET is a .NET layer on top of the OLE layer, so it�s not as fastest and efficient as SqlServer.NET.

Q 171.. What is the wildcard character in SQL?

Ans: - Let�s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve �La%�.

Q 172 Explain ACID rule of thumb for transactions?

Ans: - A transaction must be:

1. Atomic - it is one unit of work and does not dependent on previous and following transactions.

2. Consistent - data is either committed or roll back, no �in-between� case where something has been updated and something hasn�t.

3. Isolated - no transaction sees the intermediate results of the current transaction).

4. Durable - the values persist if the data had been committed even if the system crashes right after.


Ans :- Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).


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Ans:-Windows Authentication is trusted because the username and password are checked with the Active Directory; the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.



Q 176. What does the Initial Catalog parameter define in the connection string?


Q 177. What is the data provider name to connect to an Access database?

Ans: - Microsoft.Access.

Q 178. What does the Dispose method do with the connection object?


1. To do: answer better. The current answer is not entirely correct.


Ans: - Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.


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C#, .NET, XML, IIS - Interview Questions

(Framework) Q 1. What is .NET Framework?

Ans :- The .NET Framework has two main components: the common language runtime and the .NET Framework class library. You can think of the runtime as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that ensure security and robustness. The class library is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.

Q 2. What is CLR, CTS, and CLS?

Ans: - The .NET Framework provides a runtime environment called the Common Language Runtime or CLR (similar to the Java Virtual Machine or JVM in Java), which handles the execution of code and provides useful services for the implementation of the program. CLR takes care of code management at program execution and provides various beneficial services such as memory management, thread management, security management, code verification, compilation, and other system services. The managed code that targets CLR benefits from useful features such as cross-language integration, cross-language exception handling, versioning, enhanced security, deployment support, and debugging. Common Type System (CTS) describes how types are declared, used and managed in the runtime and facilitates cross-language integration, type safety, and high performance code execution. The CLS is simply a specification that defines the rules to support language integration in such a way that programs written in any language, yet can interoperate with one another, taking full advantage of inheritance, polymorphism, exceptions, and other features. These rules and the specification are documented in the ECMA proposed standard document, "Partition I Architecture", http://msdn.microsoft.com/net/ecma/


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Q 3. What are the new features of Framework 1.1 ?

Ans: - Native Support for Developing Mobile Web Applications

Q 4. Enable Execution of Windows Forms Assemblies Originating from the Internet?

Ans :- Assemblies originating from the Internet zone�for example, Microsoft Windows® Forms controls embedded in an Internet-based Web page or Windows Forms assemblies hosted on an Internet Web server and loaded either through the Web browser or programmatically using the System.Reflection.Assembly.LoadFrom () method�now receive sufficient permission to execute in a semi-trusted manner. Default security policy has been changed so that assemblies assigned by the common language runtime (CLR) to the Internet zone code group now receive the constrained permissions associated with the Internet permission set. In the .NET Framework 1.0 Service Pack 1 and Service Pack 2, such applications received the permissions associated with the Nothing permission set and could not execute.

Q 5. Enable Code Access Security for ASP.NET Applications ?

Ans :- Systems administrators can now use code access security to further lock down the permissions granted to ASP.NET Web applications and Web services. Although the operating system account under which an application runs imposes security restrictions on the application, the code access security system of the CLR can enforce additional restrictions on selected application resources based on policies specified by systems administrators. You can use this feature in a shared server environment (such as an Internet service provider (ISP) hosting multiple Web applications on one server) to isolate separate applications from one another, as well as with stand-alone servers where you want applications to run with the minimum necessary privileges.

Native Support for Communicating with ODBC and Oracle Databases

Unified Programming Model for Smart Client Application Development The Microsoft .NET Compact Framework brings the CLR, Windows Forms controls, and other .NET Framework features to small devices. The .NET Compact Framework supports a large subset of the .NET Framework class library optimized for small devices.


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Support for IPv6 the .NET Framework 1.1 supports the emerging update to the Internet Protocol, commonly referred to as IP version 6, or simply IPv6. This protocol is designed to significantly increase the address space used to identify communication endpoints in the Internet to accommodate its ongoing growth. http://msdn.microsoft.com/netframework/technologyinfo/Overview/whatsnew.aspx Q 6. Is .NET a runtime service or a development platform?

Ans :- Ans: It's both and actually a lot more. Microsoft .NET includes a new way of delivering software and services to businesses and consumers. A part of Microsoft.NET is the .NET Frameworks. The .NET frameworks SDK consists of two parts: the .NET common language runtime and the .NET class library. In addition, the SDK also includes command-line compilers for C#, C++, JScript, and VB. You use these compilers to build applications and components. These components require the runtime to execute so this is a development platform.

Q 7. What is MSIL, IL?

Ans :- When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Microsoft intermediate language (MSIL) is a language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.

Q 8. Can I write IL programs directly?

Ans :- Yes. Peter Drayton posted this simple example to the DOTNET mailing list: .assembly MyAssembly {} .class MyApp { .method static void Main() { .entrypoint


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ldstr "Hello, IL!" call void System.Console::WriteLine(class System.Object) ret } } Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.

Q 7. What is JIT (just in time)? how it works?

Ans :- Before Microsoft intermediate language (MSIL) can be executed, it must be converted by a .NET Framework just-in-time (JIT) compiler to native code, which is CPU-specific code that runs on the same computer architecture as the JIT compiler. Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as it is needed during execution and stores the resulting native code so that it is accessible for subsequent calls. The runtime supplies another mode of compilation called install-time code generation. The install-time code generation mode converts MSIL to native code just as the regular JIT compiler does, but it converts larger units of code at a time, storing the resulting native code for use when the assembly is subsequently loaded and executed. As part of compiling MSIL to native code, code must pass a verification process unless an administrator has established a security policy that allows code to bypass verification. Verification examines MSIL and metadata to find out whether the code can be determined to be type safe, which means that it is known to access only the memory locations it is authorized to access.

Q 9. What is strong name?

Ans :- A name that consists of an assembly's identity�its simple text name, version number, and culture information (if provided)�strengthened by a public key and a digital signature generated over the assembly.


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Q 10. What is portable executable (PE)?

Ans :- The file format defining the structure that all executable files (EXE) and Dynamic Link Libraries (DLL) must use to allow them to be loaded and executed by Windows. PE is derived from the Microsoft Common Object File Format (COFF). The EXE and DLL files created using the .NET Framework obey the PE/COFF formats and also add additional header and data sections to the files that are only used by the CLR. The specification for the PE/COFF file formats is available at http://www.microsoft.com/whdc/hwdev/hardware/pecoffdown.mspx

Q 11. What is Event - Delegate? clear syntax for writing a event delegate?

Ans :- The event keyword lets you specify a delegate that will be called upon the occurrence of some "event" in your code. The delegate can have one or more associated methods that will be called when your code indicates that the event has occurred. An event in one program can be made available to other programs that target the .NET Framework Common Language Runtime. // keyword_delegate.cs // delegate declaration delegate void MyDelegate(int i); class Program { public static void Main() { TakesADelegate(new MyDelegate(DelegateFunction)); } public static void TakesADelegate(MyDelegate SomeFunction) { SomeFunction(21); } public static void DelegateFunction(int i) { System.Console.WriteLine("Called by delegate with number: {0}.", i); } }


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Q 12. What is Code Access Security (CAS)?

Ans:- CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.

Q 13. How does CAS work?

Ans :- The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set. For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.)

Q 14. Who defines the CAS code groups?

Ans :- Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my syystem it looks like this: Level = Machine Code Groups: 1. All code: Nothing 1.1. Zone - MyComputer: FullTrust 1.1.1. Honor SkipVerification requests: SkipVerification 1.2. Zone - Intranet: LocalIntranet

1.3. Zone - Internet: Internet 1.4. Zone - Untrusted: Nothing

1.5. Zone - Trusted: Internet 1.6. StrongName �

0024000004800000940000000602000000240000525341310004000003 000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06 F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08


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07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C AC1DF1734633C602F8F2D5: Everything Note the hierarchy of code groups - the top of the hierarchy is the most general ('All code'), which is then sub-divided into several groups, each of which in turn can be sub-divided. Also note that (somewhat counter-intuitively) a sub-group can be associated with a more permissive permission set than its parent. Q 15. How do I define my own code group? Ans :- Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this: caspol -ag 1.3 -site www.mydomain.com FullTrust Now if you run caspol -lg you will see that the new group has been added as group 1.3.1: ... 1.3. Zone - Internet: Internet 1.3.1. Site - www.mydomain.com: FullTrust ... Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it. Q 16. How do I change the permission set for a code group? Ans :- Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this: caspol -cg 1.2 FullTrust Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect. Q 17. I'm having some trouble with CAS. How can I diagnose my

problem? Ans :- Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol -


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rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol -rsp. Q 18. I can't be bothered with all this CAS stuff. Can I turn it off? Ans :- Yes, as long as you are an administrator. Just run: caspol -s off http://www.codeproject.com/dotnet/UB_CAS_NET.asp Q 19. Which namespace is the base class for .net Class library?

Ans :- system.object

Q 20. What are object pooling and connection pooling and difference? Where do we set the Min and Max Pool size for connection pooling?

Ans :- Object pooling is a COM+ service that enables you to reduce the overhead of creating each object from scratch. When an object is activated, it is pulled from the pool. When the object is deactivated, it is placed back into the pool to await the next request. You can configure object pooling by applying the ObjectPoolingAttribute attribute to a class that derives from the System.EnterpriseServices.ServicedComponent class. Object pooling lets you control the number of connections you use, as opposed to connection pooling, where you control the maximum number reached. Following are important differences between object pooling and connection pooling:

Creation. When using connection pooling, creation is on the same thread, so if there is nothing in the pool, a connection is created on your behalf. With object pooling, the pool might decide to create a new object. However, if you have already reached your maximum, it instead gives you the next available object. This is crucial behavior when it takes a long time to create an object, but you do not use it for very long.

Enforcement of minimums and maximums. This is not done in connection pooling. The maximum value in object pooling is very important when trying to scale your application. You might need to multiplex thousands of requests to just a few objects. (TPC/C benchmarks rely on this.)


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COM+ object pooling is identical to what is used in .NET Framework managed SQL Client connection pooling. For example, creation is on a different thread and minimums and maximums are enforced. Q 21. What is Application Domain?

Ans :- The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn't scale well. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory - all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other's memory. Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages. MarshalByRefObject is the base class for objects that communicate across application domain boundaries by exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by value. When a remote application references a marshal by value object, a copy of the object is passed across application domain boundaries.

Q 22. How does an AppDomain get created?

Ans :- AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application. AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name the executable 'appdomaintest.exe' for this code to work as-is. using System; using System.Runtime.Remoting; public class CAppDomainInfo : MarshalByRefObject { public string GetAppDomainInfo()


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{ return "AppDomain = " AppDomain.CurrentDomain.FriendlyName; } } public class App { public static int Main() { AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null ); ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" ); CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap()); string info = adInfo.GetAppDomainInfo(); Console.WriteLine( "AppDomain info: " + info ); return 0; } } Q 23. What is serialization in .NET? What are the ways to control

serialization?

Ans :- Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database).Serialization can be defined as the process of storing the state of an object to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, are converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created.

Binary serialization preserves type fidelity, which is useful for preserving the state of an object between different invocations of an application. For example, you can share an object between different applications by serializing it to the clipboard. You can serialize an object to a stream, disk, memory, over the network, and so forth. Remoting uses serialization


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to pass objects "by value" from one computer or application domain to another.

XML serialization serializes only public properties and fields and does not preserve type fidelity. This is useful when you want to provide or consume data without restricting the application that uses the data. Because XML is an open standard, it is an attractive choice for sharing data across the Web. SOAP is an open standard, which makes it an attractive choice. There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code. Q 24. Why do I get errors when I try to serialize a Hashtable? Ans :- XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction. Q 25. Q 38. What is exception handling?

Ans :- When an exception occurs, the system searches for the nearest catch clause that can handle the exception, as determined by the run-time type of the exception. First, the current method is searched for a lexically enclosing try statement, and the associated catch clauses of the try statement are considered in order. If that fails, the method that called the current method is searched for a lexically enclosing try statement that encloses the point of the call to the current method. This search continues until a catch clause is found that can handle the current exception, by naming an exception class that is of the same class, or a base class, of the run-time type of the exception being thrown. A catch clause that doesn't name an exception class can handle any exception. Once a matching catch clause is found, the system prepares to transfer control to the first statement of the catch clause. Before execution of the catch clause begins, the system first executes, in order, any finally clauses that were associated with try statements more nested that than the one that caught the exception. Exceptions that occur during destructor execution are worth special mention. If an exception occurs during destructor execution, and that exception is not caught, then the execution of that destructor is terminated and the destructor of the base class (if any) is called. If there


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is no base class (as in the case of the object type) or if there is no base class destructor, then the exception is discarded.

Q 26. What is Assembly?

Ans :-Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly. Assemblies are a fundamental part of programming with the .NET Framework. An assembly performs the following functions:

It contains code that the common language runtime executes. Microsoft intermediate language (MSIL) code in a portable executable (PE) file will not be executed if it does not have an associated assembly manifest. Note that each assembly can have only one entry point (that is, DllMain, WinMain, or Main).

It forms a security boundary. An assembly is the unit at which permissions are requested and granted.

It forms a type boundary. Every type's identity includes the name of the assembly in which it resides. A type called MyType loaded in the scope of one assembly is not the same as a type called MyType loaded in the scope of another assembly.

It forms a reference scope boundary. The assembly's manifest contains assembly metadata that is used for resolving types and satisfying resource requests. It specifies the types and resources that are exposed outside the assembly. The manifest also enumerates other assemblies on which it depends.

It forms a version boundary. The assembly is the smallest versionable unit in the common language runtime; all types and resources in the same assembly are versioned as a unit. The assembly's manifest describes the version dependencies you specify for any dependent assemblies.


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It forms a deployment unit. When an application starts, only the assemblies that the application initially calls must be present. Other assemblies, such as localization resources or assemblies containing utility classes, can be retrieved on demand. This allows applications to be kept simple and thin when first downloaded.

It is the unit at which side-by-side execution is supported. Assemblies can be static or dynamic. Static assemblies can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on). Static assemblies are stored on disk in PE files. You can also use the .NET Framework to create dynamic assemblies, which are run directly from memory and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed. There are several ways to create assemblies. You can use development tools, such as Visual Studio .NET, that you have used in the past to create .dll or .exe files. You can use tools provided in the .NET Framework SDK to create assemblies with modules created in other development environments. You can also use common language runtime APIs, such as Reflection.Emit, to create dynamic assemblies. Q 27. What are the contents of assembly?

Ans :- In general, a static assembly can consist of four elements:

The assembly manifest, which contains assembly metadata.

Type metadata.

Microsoft intermediate language (MSIL) code that implements the types.

A set of resources.

Q 28. Q 41. What are the different types of assemblies?

Ans :- Private, Public/Shared, Satellite


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Q 29. What is the difference between a private assembly and a shared assembly?

Ans :- Location and visibility: A private assembly is normally used by a single application, and is stored in the application's directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes.

Versioning: The runtime enforces versioning constraints only on shared assemblies, not on private assemblies.

Q 30. What are Satellite Assemblies? How you will create this? How will you get the different language strings?

Ans :- Satellite assemblies are often used to deploy language-specific resources for an application. These language-specific assemblies work in side-by-side execution because the application has a separate product ID for each language and installs satellite assemblies in a language-specific subdirectory for each language. When uninstalling, the application removes only the satellite assemblies associated with a given language and .NET Framework version. No core .NET Framework files are removed unless the last language for that .NET Framework version is being removed. (For example, English and Japanese editions of the .NET Framework version 1.1 share the same core files. The Japanese .NET Framework version 1.1 adds satellite assemblies with localized resources in a \ja subdirectory. An application that supports the .NET Framework version 1.1, regardless of its language, always uses the same core runtime files.) http://www.ondotnet.com/lpt/a/2637 **


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Q 31. How will u load dynamic assembly? How will create assemblies at run time? What is Assembly manifest? what all details the assembly manifest will contain?

Ans :- Every assembly, whether static or dynamic, contains a collection of data that describes how the elements in the assembly relate to each other. The assembly manifest contains this assembly metadata. An assembly manifest contains all the metadata needed to specify the assembly's version requirements and security identity, and all metadata needed to define the scope of the assembly and resolve references to resources and classes. The assembly manifest can be stored in either a PE file (an .exe or .dll) with Microsoft intermediate language (MSIL) code or in a standalone PE file that contains only assembly manifest information. It contains Assembly name, Version number, Culture, Strong name information, List of all files in the assembly, Type reference information, Information on referenced assemblies.

Q 32. Difference between assembly manifest & metadata?

Ans :- assembly manifest - An integral part of every assembly that renders the assembly self-describing. The assembly manifest contains the assembly's metadata. The manifest establishes the assembly identity, specifies the files that make up the assembly implementation, specifies the types and resources that make up the assembly, itemizes the compile-time dependencies on other assemblies, and specifies the set of permissions required for the assembly to run properly. This information is used at run time to resolve references, enforce version binding policy, and validate the integrity of loaded assemblies. The self-describing nature of assemblies also helps makes zero-impact install and XCOPY deployment feasible. metadata - Information that describes every element managed by the common language runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.


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Q 33. What is Global Assembly Cache (GAC) and what is the purpose of it? (How to make an assembly to public? Steps) How more than one version of an assembly can keep in same place?

Ans :-Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. You should share assemblies by installing them into the global assembly cache only when you need to. Steps - Create a strong name using sn.exe tool eg: sn -k keyPair.snk - with in AssemblyInfo.cs add the generated file name eg: [assembly: AssemblyKeyFile("abc.snk")] - recompile project, then install it to GAC by either drag & drop it to assembly folder (C:\WINDOWS\assembly OR C:\WINNT\assembly) (shfusion.dll tool) or gacutil -i abc.dll

Q 34. If I have more than one version of one assemblies, then how'll I use old version (how/where to specify version number?)in my application? **

Q 35. How to find methods of a assembly file (not using ILDASM)?

Ans :- Reflection

Q 36. What is Garbage Collection in .Net? Garbage collection process?

Ans :- The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.


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Q 37. What is Reflection in .NET? Namespace? How will you load an assembly which is not referenced by current assembly?

Ans :- All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly. Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries. Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).

Q 38. What is Custom attribute? How to create? If I'm having custom attribute in an assembly, how to say that name in the code?

Ans :- The primary steps to properly design custom attribute classes are as follows:

Applying the AttributeUsageAttribute ([AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)])

Declaring the attribute. (class public class MyAttribute : System.Attribute { // . . . })

Declaring constructors (public MyAttribute(bool myvalue) { this.myvalue = myvalue; })

Declaring properties public bool MyProperty { get {return this.myvalue;} set {this.myvalue = value;} }

The following example demonstrates the basic way of using reflection to get access to custom attributes.


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class MainClass { public static void Main() { System.Reflection.MemberInfo info = typeof(MyClass); object[] attributes = info.GetCustomAttributes(); for (int i = 0; i < attributes.Length; i ++) { System.Console.WriteLine(attributes[i]); } } }

Q 39. What is the managed and unmanaged code in .net?

Ans :- The .NET Framework provides a run-time environment called the Common Language Runtime, which manages the execution of code and provides services that make the development process easier. Compilers and tools expose the runtime's functionality and enable you to write code that benefits from this managed execution environment. Code that you develop with a language compiler that targets the runtime is called managed code; it benefits from features such as cross-language integration, cross-language exception handling, enhanced security, versioning and deployment support, a simplified model for component interaction, and debugging and profiling services.

Q 40. How do you create threading in .NET? What is the namespace for that?

Ans :- System.Threading.Thread

Q 41. Serialize and MarshalByRef?

Ans :- using directive vs using statement You create an instance in a using statement to ensure that Dispose is called on the object when the using statement is exited. A using statement can be exited either when the end of the using statement is reached or if, for example, an exception is thrown and control leaves the statement block before the end of the statement. The using directive has two uses:


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Create an alias for a namespace (a using alias).

Permit the use of types in a namespace, such that, you do not have to qualify the use of a type in that namespace (a using directive).

Q 42. Describe the Managed Execution Process?

Ans :- The managed execution process includes the following steps:

Choosing a compiler. To obtain the benefits provided by the common language runtime, you must use one or more language compilers that target the runtime.

Compiling your code to Microsoft intermediate language (MSIL). Compiling translates your source code into MSIL and generates the required metadata.

Compiling MSIL to native code. At execution time, a just-in-time (JIT) compiler translates the MSIL into native code. During this compilation, code must pass a verification process that examines the MSIL and metadata to find out whether the code can be determined to be type safe.

Executing your code. The common language runtime provides the infrastructure that enables execution to take place as well as a variety of services that can be used during execution.

Q 43. What is Active Directory? What is the namespace used to access the Microsoft Active Directories? What are ADSI Directories?

Ans :- Active Directory Service Interfaces (ADSI) is a programmatic interface for Microsoft Windows Active Directory. It enables your applications to interact with diverse directories on a network, using a single interface. Visual Studio .NET and the .NET Framework make it easy to add ADSI functionality with the DirectoryEntry and DirectorySearcher components. Using ADSI, you can create applications that perform common


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administrative tasks, such as backing up databases, accessing printers, and administering user accounts. ADSI makes it possible for you to:

Log on once to work with diverse directories. The DirectoryEntry component class provides username and password properties that can be entered at runtime and communicated to the Active Directory object you are binding to.

Use a single application programming interface (API) to perform tasks on multiple directory systems by offering the user a variety of protocols to use. The DirectoryServices namespace provides the classes to perform most administrative functions.

Perform "rich querying" on directory systems. ADSI technology allows for searching for an object by specifying two query dialects: SQL and LDAP.

Access and use a single, hierarchical structure for administering and maintaining diverse and complicated network configurations by accessing an Active Directory tree.

Integrate directory information with databases such as SQL Server. The DirectoryEntry path may be used as an ADO.NET connection string provided that it is using the LDAP provider. using System.DirectoryServices; Q 44. How Garbage Collector (GC) Works?

Ans :- The methods in this class influence when an object is garbage collected and when resources allocated by an object are released. Properties in this class provide information about the total amount of memory available in the system and the age category, or generation, of memory allocated to an object. Periodically, the garbage collector performs garbage collection to reclaim memory allocated to objects for which there are no valid references. Garbage collection happens automatically when a request for memory cannot be satisfied using available free memory. Alternatively, an application can force garbage collection using the Collect method. Garbage collection consists of the following steps:

The garbage collector searches for managed objects that are referenced in managed code.


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The garbage collector attempts to finalize objects that are not referenced.

The garbage collector frees objects that are not referenced and reclaims their memory.

Q 45. Why do we need to call CG.SupressFinalize?

Ans :- Requests that the system not call the finalizer method for the specified object. public static void SuppressFinalize( object obj ); The method removes obj from the set of objects that require finalization. The obj parameter is required to be the caller of this method. Objects that implement the IDisposable interface can call this method from the IDisposable.Dispose method to prevent the garbage collector from calling Object.Finalize on an object that does not require it.

Q 46. What is nmake tool?

Ans :- The Nmake tool (Nmake.exe) is a 32-bit tool that you use to build projects based on commands contained in a .mak file. usage : nmake -a all

Q 47. What are Namespaces?

Ans :-The namespace keyword is used to declare a scope. This namespace scope lets you organize code and gives you a way to create globally-unique types. Even if you do not explicitly declare one, a default namespace is created. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace. Namespaces implicitly have public access and this is not modifiable.

Q 48. What is the difference between CONST and READONLY?

Ans :- Both are meant for constant values. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used. readonly int b; public X()


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{ b=1; } public X(string s) { b=5; } public X(string s, int i) { b=i; } Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants, as in the following example: public static readonly uint l1 = (uint) DateTime.Now.Ticks; (this can't be possible with const)

Q 49. What is the difference between ref & out parameters?

Ans :- An argument passed to a ref parameter must first be initialized. Compare this to an out parameter, whose argument does not have to be explicitly initialized before being passed to an out parameter.

Q 50. What is the difference between Array and LinkedList?What is the difference between Array and Arraylist?

Ans :- As elements are added to an ArrayList, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize or by setting the Capacity property explicitly.

Q 51. What is Jagged Arrays?

Ans :- A jagged array is an array whose elements are arrays. The elements of a jagged array can be of different dimensions and sizes. A jagged array is sometimes called an "array-of-arrays."

Q 52. What are indexers?

Ans :- Indexers are similar to properties, except that the get and set accessors of indexers take parameters, while property accessors do not.


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(COM) Q 53. What is Interop Services?

Ans :- The common language runtime provides two mechanisms for interoperating with unmanaged code:

Platform invoke, which enables managed code to call functions exported from an unmanaged library.

COM interop, which enables managed code to interact with COM objects through interfaces. Both platform invoke and COM interop use interop marshaling to accurately move method arguments between caller and callee and back, if required. Q 54. How does u handle this COM components developed in other

programming languages in .NET?

Q 55. What is RCW (Runtime Callable Wrappers)?

Ans :- The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object.

Q 56. What is CCW (COM Callable Wrapper) ? Ans :- proxy object generated by the common language runtime so that existing COM applications can use managed classes, including .NET Framework classes, transparently. Q 57. Q 68. How CCW and RCW is working?

**

Q 58. How will you register com+ services?

Ans :- The .NET Framework SDK provides the .NET Framework Services Installation Tool (Regsvcs.exe - a command-line tool) to manually register an assembly containing serviced components. You can also access these


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registration features programmatically with the System.EnterpriseServicesRegistrationHelper class by creating an instance of class RegistrationHelper and using the method InstallAssembly

Q 59. What is use of ContextUtil class?

Ans :- ContextUtil is the preferred class to use for obtaining COM+ context information.

Q 60. What is Pinvoke?

Ans :- Platform invoke is a service that enables managed code to call unmanaged functions implemented in dynamic-link libraries (DLLs), such as those in the Win32 API. It locates and invokes an exported function and marshals its arguments (integers, strings, arrays, structures, and so on) across the interoperation boundary as needed.

Q 61. Is it true that COM objects no longer need to be registered on the server?

Ans :- Answer: Yes and No. Legacy COM objects still need to be registered on the server before they can be used. COM developed using the new .NET Framework will not need to be registered. Developers will be able to auto-register these objects just by placing them in the 'bin' folder of the application.

Q 62. Can .NET Framework components use the features of Component Services?

Ans:- Yes, you can use the features and functions of Component Services from a .NET Framework component. http://msdn.microsoft.com/library/techart/Pahlcompserv.htm

(OOPS) Q 63. What are the OOPS concepts?

Ans :- 1) Encapsulation: It is the mechanism that binds together code and data in manipulates, and keeps both safe from outside interference and


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misuse. In short it isolates a particular code and data from all other codes and data. A well-defined interface controls the access to that particular code and data. 2) Inheritance: It is the process by which one object acquires the properties of another object. This supports the hierarchical classification. Without the use of hierarchies, each object would need to define all its characteristics explicitly. However, by use of inheritance, an object need only define those qualities that make it unique within its class. It can inherit its general attributes from its parent. A new sub-class inherits all of the attributes of all of its ancestors. 3) Polymorphism: It is a feature that allows one interface to be used for general class of actions. The specific action is determined by the exact nature of the situation. In general polymorphism means "one interface, multiple methods", This means that it is possible to design a generic interface to a group of related activities. This helps reduce complexity by allowing the same interface to be used to specify a general class of action. It is the compiler's job to select the specific action (that is, method) as it applies to each situation.

Q 64. What is the difference between a Struct and a Class?

Ans :- The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive.

When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized.

It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values.

It is an error to initialize an instance field in a struct.


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There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do.

A struct is a value type, while a class is a reference type.

Q 65. Value type & reference types difference? Example from .NET. Integer & struct are value types or reference types in .NET?

Ans: -Most programming languages provide built-in data types, such as integers and floating-point numbers, that are copied when they are passed as arguments (that is, they are passed by value). In the .NET Framework, these are called value types. The runtime supports two kinds of value types:

Built-in value types The .NET Framework defines built-in value types, such as System.Int32 and System.Boolean, which correspond and are identical to primitive data types used by programming languages.

User-defined value types Your language will provide ways to define your own value types, which derive from System.ValueType. If you want to define a type representing a value that is small, such as a complex number (using two floating-point numbers), you might choose to define it as a value type because you can pass the value type efficiently by value. If the type you are defining would be more efficiently passed by reference, you should define it as a class instead. Variables of reference types, referred to as objects, store references to the actual data. This following are the reference types: class

interface

delegate This following are the built-in reference types: object

string


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Q 66. What is Method overloading?

Ans:- Method overloading occurs when a class contains two methods with the same name, but different signatures.

Q 67. What is Method Overriding? How to override a function in C#?

Ans:- Use the override modifier to modify a method, a property, an indexer, or an event. An override method provides a new implementation of a member inherited from a base class. The method overridden by an override declaration is known as the overridden base method. The overridden base method must have the same signature as the override method. You cannot override a non-virtual or static method. The overridden base method must be virtual, abstract, or override.

Q 68. Can we call a base class method without creating instance?

Ans :- Its possible If its a static method. Its possible by inheriting from that class also. Its possible from derived classes using base keyword.

Q 69. You have one base class virtual function how will call that function from derived class? Ans:

class a { public virtual int m() { return 1; } } class b:a { public int j() { return m(); } }


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Q 70. In which cases you use override and new base?

Ans :- Use the new modifier to explicitly hide a member inherited from a base class. To hide an inherited member, declare it in the derived class using the same name, and modify it with the new modifier.

C# Language features Q 71. What are Sealed Classes in C#?

Ans :- The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified as the base class of another class. (A sealed class cannot also be an abstract class)

Q 72. What is Polymorphism? How does VB.NET/C# achieve polymorphism?

Ans :- class Token { public string Display() { //Implementation goes here return "base"; } } class IdentifierToken:Token { public new string Display() //What is the use of new keyword { //Implementation goes here return "derive"; } } static void Method(Token t) { Console.Write(t.Display()); } public static void Main() {


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IdentifierToken Variable=new IdentifierToken(); Method(Variable); //Which Class Method is called here Console.ReadLine(); } For the above code What is the "new" keyword and Which Class Method is called here A: it will call base class Display method class Token { public virtual string Display() { //Implementation goes here return "base"; } } class IdentifierToken:Token { public override string Display() //What is the use of new keyword { //Implementation goes here return "derive"; } } static void Method(Token t) { Console.Write(t.Display()); } public static void Main() { IdentifierToken Variable=new IdentifierToken(); Method(Variable); //Which Class Method is called here Console.ReadLine(); } A: Derive


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Q 73. In which Scenario you will go for Interface or Abstract Class?

Ans :- Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes. Even though class inheritance allows your classes to inherit implementation from a base class, it also forces you to make most of your design decisions when the class is first published. Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code.

Interfaces vs. Abstract Classes Feature Interface Abstract class

Multiple inheritance

A class may implement several interfaces.

A class may extend only one abstract class.

Default implementation

An interface cannot provide any code at all, much less default code.

An abstract class can provide complete code, default code, and/or just stubs that have to be overridden.

Constants

Static final constants only, can use them without qualificat

Both instance and static constants are possible. Both static and instance intialiser code


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ion in classes that implement the interface. On the other paw, these unqualified names pollute the namespace. You can use them and it is not obvious where they are coming from since the qualification is optional.

are also possible to compute the constants.

Third party convenience

An interface implementation may be added to any existing third party class.

A third party class must be rewritten to extend only from the abstract class.


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is-a vs -able or can-do

Interfaces are often used to describe the peripheral abilities of a class, not its central identity, e.g. an Automobile class might implement the Recyclable interface, which could apply to many otherwise totally unrelated objects

An abstract class defines the core identity of its descendants. If you defined a Dog abstract class then Damamation descendants are Dogs, they are not merely dogable. Implemented interfaces enumerate the general things a class can do, not the things a class is.


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Plug-in

You can write a new replacement module for an interface that contains not one stick of code in common with the existing implementations. When you implement the interface, you start from scratch without any default implementation. You have to obtain your tools from other classes; nothing comes with the interface other than a few constants. This gives you freedom to implement a radically different internal design.

You must use the abstract class as-is for the code base, with all its attendant baggage, good or bad. The abstract class author has imposed structure on you. Depending on the cleverness of the author of the abstract class, this may be good or bad. Another issue that's important is what I call "heterogeneousvs. homogeneous." If implementors/subclasses are homogeneous, tend towards an abstract base class. If they are heterogeneous, use an interface. (Now all I haveto do is come up with a good definition of hetero/homogeneous in this context.) If the various objects are all of-a-kind, and share a common state


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Homogeneity

If all the various implementations share is the method signatures, then an interface works best.

If the various implementations are all of a kind and share a common status and behavior, usually an abstract class works best.

Maintenance

If your client code talks only in terms of an interface, you can easily change the concrete implementation behind it, using a factory method.

Just like an interface, if your client code talks only in terms of an abstract class, you can easily change the concrete implementation behind it, using a factory method.

Speed

Slow, requires extra indirection to find the corresponding

Fast


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method in the actual class. Modern JVMs are discovering ways to reduce this speed penalty.

Terseness

The constant declarations in an interface are all presumed public static final, so you may leave that part out. You can't call any methods to compute the initial values of your constants. You need not declare individual methods

You can put shared code into an abstract class, where you cannot into an interface. If interfaces want to share code, you will have to write other bubblegum to arrange that. You may use methods to compute the initial values of your constants and variables, both instance and static. You must declare all the individual methods of an


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of an interface abstract. They are all presumed so.

abstract class abstract.

Adding functionality

If you add a new method to an interface, you must track down all implementations of that interface in the universe and provide them with a concrete implementation of that method.

If you add a new method to an abstract class, you have the option of providing a default implementation of it. Then all existing code will continue to work without change.

see the code interface ICommon { int getCommon(); } interface ICommonImplements1:ICommon { }


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interface ICommonImplements2:ICommon { } public class a:ICommonImplements1,ICommonImplements2 { } Q 74. How to implement getCommon method in class a? Are you

seeingany problem in the implementation? Ans: public class a:ICommonImplements1,ICommonImplements2 { public int getCommon() { return 1; } } interface IWeather { void display(); } public class A:IWeather { public void display() { MessageBox.Show("A"); } } public class B:A { } public class C:B,IWeather { public void display() { MessageBox.Show("C"); } } Q 75. When I instantiate C.display(), will it work? Ans :- interface IPrint { string Display();


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} interface IWrite { string Display(); } class PrintDoc:IPrint,IWrite { //Here is implementation } how to implement the Display in the class printDoc (How to resolve the naming Conflict) A: no naming conflicts class PrintDoc:IPrint,IWrite { public string Display() { return "s"; } } interface IList { int Count { get; set; } } interface ICounter { void Count(int i); } interface IListCounter: IList, ICounter {} class C { void Test(IListCounter x) { x.Count(1); // Error x.Count = 1; // Error ((IList)x).Count = 1; // Ok, invokes IList.Count.set ((ICounter)x).Count(1); // Ok, invokes ICounter.Count } } Q 76. Write one code example for compile time binding and one for

run time binding? What is early/late binding?


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Ans:- An object is early bound when it is assigned to a variable declared to be of a specific object type. Early bound objects allow the compiler to allocate memory and perform other optimizations before an application executes. ' Create a variable to hold a new object. Dim FS As FileStream ' Assign a new object to the variable. FS = New FileStream("C:\tmp.txt", FileMode.Open) By contrast, an object is late bound when it is assigned to a variable declared to be of type Object. Objects of this type can hold references to any object, but lack many of the advantages of early-bound objects. Dim xlApp As Object xlApp = CreateObject("Excel.Application")

(Access specifiers) Q 77. What are the access-specifiers available in c#?

Ans :- Private, Protected, Public, Internal, Protected Internal.

Q 78. Explain about Protected and protected internal, �internal� access-specifier?

Ans :- protected - Access is limited to the containing class or types derived from the containing class. internal - Access is limited to the current assembly. protected internal - Access is limited to the current assembly or types derived from the containing class.

(Constructor / Destructor)

Q 79. Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?

Ans :- (Class constructor method is also known as type constructor or type initializer) Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before


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any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention. A static constructor is used to initialize a class. It is called automatically to initialize the class before the first instance is created or any static members are referenced.

Q 80. What is Private Constructor? and it�s use? Can you create instance of a class which has Private Constructor?

Ans :- A: When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes) Make a constructor private if: - You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method. - You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory.

Q 81. I have 3 overloaded constructors in my class. In order to avoid making instance of the class do I need to make all constructors to private?

Ans :- (yes)

Q 82. Overloaded constructor will call default constructor internally?

Ans :- (no)

Q 83. What are virtual destructors? Destructor and finalize?

Ans ;- Generally in C++ the destructor is called when objects gets destroyed. And one can explicitly call the destructors in C++. And also the objects are destroyed in reverse order that they are created in. So in C++ you have control over the destructors. In C# you can never call them, the reason is one cannot destroy an object.


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So who has the control over the destructor (in C#)? it's the .Net frameworks Garbage Collector (GC). GC destroys the objects only when necessary. Some situations of necessity are memory is exhausted or user explicitly calls System.GC.Collect() method. Points to remember: 1. Destructors are invoked automatically, and cannot be invoked explicitly. 2. Destructors cannot be overloaded. Thus, a class can have, at most, one destructor. 3. Destructors are not inherited. Thus, a class has no destructors other than the one, which may be declared in it. 4. Destructors cannot be used with structs. They are only used with classes. 5. An instance becomes eligible for destruction when it is no longer possible for any code to use the instance. 6. Execution of the destructor for the instance may occur at any time after the instance becomes eligible for destruction. 7. When an instance is destructed, the destructors in its inheritance chain are called, in order, from most derived to least derived. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconfinalizemethodscdestructors.asp

Q 84. What is the difference between Finalize and Dispose (Garbage collection)?

Ans :- Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object. In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method


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when it is done using the object. Dispose can be called even if other references to the object are alive. Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose.

Q 85. What is close method? How its different from Finalize & Dispose?

Q 86. What is boxing & unboxing?

Q 87. What is check/uncheck?

Q 88. What is the use of base keyword? Tell me a practical example for base keyword�s usage?

Q 89. What are the different .net tools which u used in projects?

Ans : -

Try

{ ... } catch { ...//exception occurred here. What'll happen? } finally { .. } Ans : It will throw exception.


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Q 90. What will do to avoid prior case?

Ans:-

try { try { ... } catch { ... //exception occurred here. } finally

{ ... } } catch { ... } finally { ... } try { ... } catch { ... } finally {


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.. } Q 91. Will it go to finally block if there is no exception happened? Ans: Yes. The finally block is useful for cleaning up any resources allocated in the try block. Control is always passed to the finally block regardless of how the try block exits. Q 92. Is goto statement supported in C#? How about Java?

Ans :- Gotos are supported in C#to the fullest. In Java goto is a reserved keyword that provides absolutely no functionality.

Q 93. What�s different about switch statements in C#?

Ans : - No fall-throughs allowed. Unlike the C++ switch statement, C# does not support an explicit fall through from one case label to another. If you want, you can use goto a switch-case, or goto default. case 1: cost += 25; break; case 2: cost += 25; goto case 1; (ADO.NET) Q 94. Advantage of ADO.Net?

Ans :-

ADO.NET Does Not Depend On Continuously Live Connections

Database Interactions Are Performed Using Data Commands

Data Can Be Cached in Datasets

Datasets Are Independent of Data Sources

Data Is Persisted as XML

Schemas Define Data Structures


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Q 95. How would u connect to database using .NET?

Ans :-

SqlConnection nwindConn = new SqlConnection("Data Source=localhost; Integrated Security=SSPI;" + "Initial Catalog=northwind"); nwindConn.Open();

Q 96. What are relation objects in dataset and how & where to use them?

Ans : - In a DataSet that contains multiple DataTable objects, you can use DataRelation objects to relate one table to another, to navigate through the tables, and to return child or parent rows from a related table. Adding a DataRelation to a DataSet adds, by default, a UniqueConstraint to the parent table and a ForeignKeyConstraint to the child table. The following code example creates a DataRelation using two DataTable objects in a DataSet. Each DataTable contains a column named CustID, which serves as a link between the two DataTable objects. The example adds a single DataRelation to the Relations collection of the DataSet. The first argument in the example specifies the name of the DataRelation being created. The second argument sets the parent DataColumn and the third argument sets the child DataColumn. custDS.Relations.Add("CustOrders", custDS.Tables["Customers"].Columns["CustID"], custDS.Tables["Orders"].Columns["CustID"]); OR private void CreateRelation() { // Get the DataColumn objects from two DataTable objects in a DataSet. DataColumn parentCol; DataColumn childCol; // Code to get the DataSet not shown here. parentCol = DataSet1.Tables["Customers"].Columns["CustID"]; childCol = DataSet1.Tables["Orders"].Columns["CustID"]; // Create DataRelation.


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DataRelation relCustOrder; relCustOrder = new DataRelation("CustomersOrders", parentCol, childCol); // Add the relation to the DataSet. DataSet1.Relations.Add(relCustOrder); }

Q 97. Difference between OLEDB Provider and SqlClient ?

Ans :- Ans: SQLClient .NET classes are highly optimized for the .net / sqlserver combination and achieve optimal results. The SqlClient data provider is fast. It's faster than the Oracle provider, and faster than accessing database via the OleDb layer. It's faster because it accesses the native library (which automatically gives you better performance), and it was written with lots of help from the SQL Server team.

Q 98. What are the different namespaces used in the project to connect the database? What data providers available in .net to connect to database?

Ans :- System.Data.OleDb � classes that make up the .NET Framework Data Provider for OLE DB-compatible data sources. These classes allow you to connect to an OLE DB data source, execute commands against the source, and read the results.

System.Data.SqlClient � classes that make up the .NET Framework Data Provider for SQL Server, which allows you to connect to SQL Server 7.0, execute commands, and read results. The System.Data.SqlClient namespace is similar to the System.Data.OleDb namespace, but is optimized for access to SQL Server 7.0 and later.

System.Data.Odbc - classes that make up the .NET Framework Data Provider for ODBC. These classes allow you to access ODBC data source in the managed space.

System.Data.OracleClient - classes that make up the .NET Framework Data Provider for Oracle. These classes allow you to access an Oracle data source in the managed space.


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Q 99. Difference between DataReader and DataAdapter / DataSet and DataAdapter?

Ans :- You can use the ADO.NET DataReader to retrieve a read-only, forward-only stream of data from a database. Using the DataReader can increase application performance and reduce system overhead because only one row at a time is ever in memory. After creating an instance of the Command object, you create a DataReader by calling Command.ExecuteReader to retrieve rows from a data source, as shown in the following example. SqlDataReader myReader = myCommand.ExecuteReader(); You use the Read method of the DataReader object to obtain a row from the results of the query. while (myReader.Read()) Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1)); myReader.Close(); The DataSet is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple and differing data sources, used with XML data, or used to manage data local to the application. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables. The methods and objects in a DataSet are consistent with those in the relational database model. The DataSet can also persist and reload its contents as XML and its schema as XML Schema definition language (XSD) schema. The DataAdapter serves as a bridge between a DataSet and a data source for retrieving and saving data. The DataAdapter provides this bridge by mapping Fill, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet. If you are connecting to a Microsoft SQL Server database, you can increase overall performance by using the SqlDataAdapter along with its associated SqlCommand and SqlConnection. For other OLE DB-supported databases, use the DataAdapter with its associated OleDbCommand and OleDbConnection objects.

Q 100. Which method do you invoke on the DataAdapter control to load your generated dataset with data?

Ans :- Fill()


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Q 101. Explain different methods and Properties of DataReader which you have used in your project?

Ans : -Read GetString GetInt32 while (myReader.Read()) Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1)); myReader.Close();

Q 102. What happens when we issue Dataset.ReadXml command?

Ans :-Reads XML schema and data into the DataSet.

Q 103. In how many ways we can retrieve table records count? How to find the count of records in a dataset?

Ans :- foreach(DataTable thisTable in myDataSet.Tables){ // For each row, print the values of each column. foreach(DataRow myRow in thisTable.Rows){

Q 104. How to check if a datareader is closed or opened?

Ans :- IsClosed()

Q 105. What happens when u try to update data in a dataset in .NET while the record is already deleted in SQL SERVER as backend? OR What is concurrency? How will you avoid concurrency when dealing with dataset? (One user deleted one row after that another user through his dataset was trying to update same row. What will happen? How will you avoid the problem?) **

Q 106. How do you merge 2 datasets into the third dataset in a simple manner? OR If you are executing these statements in commandObject. "Select * from Table1;Select * from Table2� how you will deal result


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set? **

Q 107. How do you sort a dataset? **

Q 108. If a dataset contains 100 rows, how to fetch rows between 5 and 15 only? **

Q 109. Differences between dataset.clone and dataset.copy?

Ans : -Clone - Copies the structure of the DataSet, including all DataTable schemas, relations, and constraints. Does not copy any data. Copy - Copies both the structure and data for this DataSet.

Q 110. What is the use of parameter object? **

Q 111. How to generate XML from a dataset and vice versa? **

Q 112. What is method to get XML and schema from Dataset?

Ans: getXML () and get Schema ()

Q 113. How do u implement locking concept for dataset? ** (ASP.NET)

Q 114. Asp.net and asp � differences?

Ans :-

Code Render Block Code Declaration Block

Compiled Request/Response Event Driven

Object Oriented - Constructors/Destruct


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ors, Inheritance, overloading..

Exception Handling - Try, Catch, Finally

Down-level Support Cultures User Controls

In-built client side validation

Session - weren't transferable across servers

It can span across servers, It can survive server crashes, can work with browsers that don't support cookies

built on top of the window & IIS, it was always a separate entity & its functionality was limited.

its an integral part of OS under the .net framework. It shares many of the same objects that traditional applications would use, and all .net objects are available for asp.net's consumption.

Garbage Collection

Declare variable with datatype

In built graphics support

Cultures Q 115. How ASP and ASP.NET page works? Explain about asp.net

page life cycle? **


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Q 116. Order of events in an asp.net page? Control Execution Lifecycle?

Ans :-

Phase What a control needs to do

Method or event to override

Initialize Initialize settings needed during the lifetime of the incoming Web request.

Init event (OnInit method)

Load view state

At the end of this phase, the ViewState property of a control is automatically populated as described in Maintaining State in a Control.

LoadViewState method


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A control can override the default implementation of the LoadViewState method to customize state restoration.

Process postback data

Process incoming form data and update properties accordingly.

LoadPostData method (if IPostBackDataHandler is implemented)

Load Perform actions common to all requests, such as setting up a database query. At this point, server controls

Load event (OnLoad method)


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in the tree are created and initialized, the state is restored, and form controls reflect client-side data.

Send postback change notifications

Raise change events in response to state changes between the current and previous postbacks.

RaisePostDataChangedEventmethod (if IPostBackDataHandler is implemented)

Handle postback events

Handle the client-side event that caused the postback and raise appropri

RaisePostBackEvent method(if IPostBackEventHandler is implemented)


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ate events on the server.

Prerender Perform any updates before the output is rendered. Any changes made to the state of the control in the prerender phase can be saved, while changes made in the rendering phase are lost.

PreRender event (OnPreRender method)

Save state

The ViewState property of a control is automatically persisted to a

SaveViewState method


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string object after this stage. This string object is sent to the client and back as a hidden variable. For improving efficiency, a control can override the SaveViewState method to modify the ViewState property.

Render Generate output to be rendered to the client.

Render method

Dispose Perform Dispose method


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any final cleanup before the control is torn down. References to expensive resources such as database connections must be released in this phase.

Unload Perform any final cleanup before the control is torn down. Control authors generally perform cleanup in Dispose and do not handle

UnLoad event (On UnLoad method)


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this event.

Note To override an EventName event, override the OnEventName method (and call base. OnEventName).

Q 117. What are server controls?

Ans :- ASP.NET server controls are components that run on the server and encapsulate user-interface and other related functionality. They are used in ASP.NET pages and in ASP.NET code-behind classes.

Q 118. What is the difference between Web User Control and Web Custom Control?

Ans :- Web custom controls are compiled components that run on the server and that encapsulate user-interface and other related functionality into reusable packages. They can include all the design-time features of standard ASP.NET server controls, including full support for Visual Studio design features such as the Properties window, the visual designer, and the Toolbox. There are several ways that you can create Web custom controls:

You can compile a control that combines the functionality of two or more existing controls. For example, if you need a control that encapsulates a button and a text box, you can create it by compiling the existing controls together.

If an existing server control almost meets your requirements but lacks some required features, you can customize the control by deriving from it and overriding its properties, methods, and events.

If none of the existing Web server controls (or their combinations) meet your requirements, you can create a custom control by deriving from one of the base control classes. These classes provide all the basic


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functionality of Web server controls, so you can focus on programming the features you need.

If none of the existing ASP.NET server controls meet the specific requirements of your applications, you can create either a Web user control or a Web custom control that encapsulates the functionality you need. The main difference between the two controls lies in ease of creation vs. ease of use at design time. Web user controls are easy to make, but they can be less convenient to use in advanced scenarios. You develop Web user controls almost exactly the same way that you develop Web Forms pages. Like Web Forms, user controls can be created in the visual designer, they can be written with code separated from the HTML, and they can handle execution events. However, because Web user controls are compiled dynamically at run time they cannot be added to the Toolbox, and they are represented by a simple placeholder glyph when added to a page. This makes Web user controls harder to use if you are accustomed to full Visual Studio .NET design-time support, including the Properties window and Design view previews. Also, the only way to share the user control between applications is to put a separate copy in each application, which takes more maintenance if you make changes to the control. Web custom controls are compiled code, which makes them easier to use but more difficult to create; Web custom controls must be authored in code. Once you have created the control, however, you can add it to the Toolbox and display it in a visual designer with full Properties window support and all the other design-time features of ASP.NET server controls. In addition, you can install a single copy of the Web custom control in the global assembly cache and share it between applications, which makes maintenance easier.

Web usercontrols Web custom controls Easier to create Harder to create Limited supportfor consumers who use a visual design tool

Full visual design tool support for consumers

A separate copy of the control is required in each application

Only a single copy of the control is required, in the global assembly cache

Cannot be added to the Toolbox in Visual Studio

Can be added to the Toolbox in Visual Studio


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Good for static layout Good for dynamic layout (Session/State) Q 119. Application and Session Events?

Ans :- The ASP.NET page framework provides ways for you to work with events that can be raised when your application starts or stops or when an individual user's session starts or stops:

Application events are raised for all requests to an application. For example, Application_BeginRequest is raised when any Web Forms page or XML Web service in your application is requested. This event allows you to initialize resources that will be used for each request to the application. A corresponding event, Application_EndRequest, provides you with an opportunity to close or otherwise dispose of resources used for the request.

Session events are similar to application events (there is a Session_OnStart and a Session_OnEnd event), but are raised with each unique session within the application. A session begins when a user requests a page for the first time from your application and ends either when your application explicitly closes the session or when the session times out. You can create handlers for these types of events in the Global.asax file. Q 120. Difference between ASP Session and ASP.NET Session?

Ans :- asp.net session supports cookie less session & it can span across multiple servers

Q 121. What is cookie less session? How it works?

Ans :- By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. If cookies are not available, a session can be tracked by adding a session identifier to the URL. This can be enabled by setting the following:


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<sessionState cookieless="true" /> http://samples.gotdotnet.com/quickstart/aspplus/doc/stateoverview.aspx

Q 122. How you will handle session when deploying application in more than a server? Describe session handling in a webfarm, how does it work and what are the limits?

Ans :- By default, ASP.NET will store the session state in the same process that processes the request, just as ASP does. Additionally, ASP.NET can store session data in an external process, which can even reside on another machine. To enable this feature:

Start the ASP.NET state service, either using the Services snap-in or by executing "net start aspnet_state" on the command line. The state service will by default listen on port 42424. To change the port, modify the registry key for the service: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\Port

Set the mode attribute of the <sessionState> section to "StateServer".

Configure the stateConnectionString attribute with the values of the machine on which you started aspnet_state. The following sample assumes that the state service is running on the same machine as the Web server ("localhost") and uses the default port (42424): <sessionState mode="StateServer" stateConnectionString="tcpip=localhost:42424" /> Note that if you try the sample above with this setting, you can reset the Web server (enter iisreset on the command line) and the session state value will persist. ** Q 123. What method do you use to explicitly kill a users session?

Ans :- Abandon()

Q 124. What are the different ways you would consider sending data across pages in ASP (i.e between 1.asp to 2.asp)?


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Ans :- Session public properties

Q 125. What is State Management in .Net and how many ways are there to maintain a state in .Net? What is view state?

Ans :- Web pages are recreated each time the page is posted to the server. In traditional Web programming, this would ordinarily mean that all information associated with the page and the controls on the page would be lost with each round trip. To overcome this inherent limitation of traditional Web programming, the ASP.NET page framework includes various options to help you preserve changes � that is, for managing state. The page framework includes a facility called view state that automatically preserves property values of the page and all the controls on it between round trips. However, you will probably also have application-specific values that you want to preserve. To do so, you can use one of the state management options. Client-Based State Management Options: View State Hidden Form Fields Cookies Query Strings Server-Based State Management Options Application State Session State Database Support

Q 126. What are the disadvantages of view state / what are the benefits?

Ans:- Automatic view-state management is a feature of server controls that enables them to repopulate their property values on a round trip (without you having to write any code). This feature does impact performance, however, since a server control's view state is passed to and from the server in a hidden form field. You should be aware of when view state helps you and when it hinders your page's performance.

Q 127. When maintaining session through Sql server, what is the impact of Read and Write operation on Session objects? will performance degrade?


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Ans:-Maintaining state using database technology is a common practice when storing user-specific information where the information store is large. Database storage is particularly useful for maintaining long-term state or state that must be preserved even if the server must be restarted. **

Q 128. What are the contents of cookie? **

Q 129. How do you create a permanent cookie? **

Q 130. What is ViewState? What does the "EnableViewState" property do? Why would I want it on or off? **

Q 131. Explain the differences between Server-side and Client-side code?

Ans :- Server side code will process at server side & it will send the result to client. Client side code (javascript) will execute only at client side.

Q 132. Can you give an example of what might be best suited to place in the Application_Start and Session_Start subroutines?

**

Q 133. Which ASP.NET configuration options are supported in the ASP.NET implementation on the shared web hosting platform?

Ans :- A: Many of the ASP.NET configuration options are not configurable at the site, application or subdirectory level on the shared hosting platform. Certain options can affect the security, performance and stability of the server and, therefore cannot be changed. The following settings are the only ones that can be changed in your site�s web.config file (s): browserCaps clientTarget pages


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customErrors globalization authorization authentication webControls webServices http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconaspnetconfiguration.asp

Q 134. Briefly describe the role of global.asax?

Q 135. How can u debug your .net application?

Q 136. How do u deploy your asp.net application?

Q 137. Where do we store our connection string in asp.net application?

Q 138. Various steps taken to optimize a web based application (caching, stored procedure etc.)

Q 139. How does ASP.NET framework maps client side events to Server side events.

(Security) Q 140. Security types in ASP/ASP.NET? Different Authentication

modes?

Q 141. How .Net has implemented security for web applications?

Q 142. How to do Forms authentication in asp.net?

Q 143. Explain authentication levels in .net ?

Q 144. Explain autherization levels in .net ?

Q 145. What is Role-Based security?


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Ans :- A role is a named set of principals that have the same privileges with respect to security (such as a teller or a manager). A principal can be a member of one or more roles. Therefore, applications can use role membership to determine whether a principal is authorized to perform a requested action. **

Q 146. How will you do windows authentication and what is the namespace? If a user is logged under integrated windows authentication mode, but he is still not able to logon, what might be the possible cause for this? In ASP.Net application how do you find the name of the logged in person under windows authentication?

Q 147. What are the different authentication modes in the .NET environment?

Ans :- <authentication mode="Windows|Forms|Passport|None"> <forms name="name" loginUrl="url" protection="All|None|Encryption|Validation"

timeout="30" path="/" > requireSSL="true|false"

slidingExpiration="true|false"> <credentials passwordFormat="Clear|SHA1|MD5"> <user name="username" password="password"/> </credentials> </forms> <passport redirectUrl="internal"/> </authentication>

Attribute Option Description

mode Controls the default authentication mode for an application.


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Windows Specifies Windows authentication as the default authentication mode. Use this mode when using any form of Microsoft Internet Information Services (IIS) authentication: Basic, Digest, Integrated Windows authentication (NTLM/Kerberos), or certificates.

Forms Specifies ASP.NET forms-based authentication as the default authentication mode.

Passport Specifies Microsoft Passport authentication as the default authentication mode.

None Specifies no authentication. Only anonymous users are expected or applications can handle events to provide their own authentication.

Q 148. How do you specify whether your data should be passed as Query string and Forms (Mainly about POST and GET)?


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Ans : - Through attribute tag of form tag.

Q 149. What is the other method, other than GET and POST, in ASP.NET?

Q 150. What are validator? Name the Validation controls in asp.net? How do u disable them? Will the asp.net validators run in server side or client side? How do you do Client-side validation in .Net? How to disable validator control by client side JavaScript?

Ans :-A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation ("EnableClientScript" property set to true/false) using client script. The following validation controls are available in asp.net: RequiredFieldValidator Control, CompareValidator Control, RangeValidator Control, RegularExpressionValidator Control, CustomValidator Control, ValidationSummary Control.

Q 151. Which two properties are there on every validation control?

Ans :- ControlToValidate, ErrorMessage

Q 152. How do you use css in asp.net?

Ans: -Within the <HEAD> section of an HTML document that will use these styles, add a link to this external CSS style sheet that follows this form: <LINK REL="STYLESHEET" TYPE="text/css" HREF="MyStyles.css"> MyStyles.css is the name of your external CSS style sheet.

Q 153. How do you implement postback with a text box? What is postback and usestate?


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Ans :- Make AutoPostBack property to true

Q 154. How can you debug an ASP page, without touching the code?

Q 155. What is SQL injection?

Ans :- An SQL injection attack "injects" or manipulates SQL code by adding unexpected SQL to a query. Many web pages take parameters from web user, and make SQL query to the database. Take for instance when a user login, web page that user name and password and make SQL query to the database to check if a user has valid name and password. Username: ' or 1=1 --- Password: [Empty] This would execute the following query against the users table: select count(*) from users where userName='' or 1=1 --' and userPass=''

Q 156. How can u handle Exceptions in Asp.Net?

Q 157. How can u handle Un Managed Code Exceptions in ASP.Net?

Q 158. Asp.net - How to find last error which occurred?

Ans :- : Server.GetLastError(); [C#] Exception LastError; String ErrMessage; LastError = Server.GetLastError(); if (LastError != null) ErrMessage = LastError.Message; else ErrMessage = "No Errors"; Response.Write("Last Error = " + ErrMessage);

Q 159. How to do Caching in ASP? A: <%@ OutputCache Duration="60" VaryByParam="None" %>

VaryByParamvalue Description


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none One version of page cached (only raw GET)

* n versions of page cached based on query string and/or POST body

v1

n versions of page cached based on value of v1 variable in query string or POST body

v1;v2

n versions of page cached based on value of v1 and v2 variables in query string or POST body

<%@ OutputCache Duration="60" VaryByParam="none" %> <%@ OutputCache Duration="60" VaryByParam="*" %> <%@ OutputCache Duration="60" VaryByParam="name;age" %> The OutputCache directive supports several other cache varying options

VaryByHeader - maintain separate cache entry for header string changes (UserAgent, UserLanguage, etc.)

VaryByControl - for user controls, maintain separate cache entry for properties of a user control

VaryByCustom - can specify separate cache entries for browser types and version or provide a custom GetVaryByCustomString method in HttpApplicationderived class

Q 160. What is the Global ASA(X) File?

Ans:- Any alternative to avoid name collisions other then Namespaces. A scenario that two namespaces named N1 and N2 are there both having the same class say A. now in another class i ve written using N1;using N2; and i am instantiating class A in this class. Then how will u avoid name collisions? Ans: using alias Eg: using MyAlias = MyCompany.Proj.Nested;


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Q 161. Which is the namespace used to write error message in event Log File?

Q 162. What are the page level transaction and class level transaction?

Q 163. What are different transaction options?

Q 164. What is the namespace for encryption?

Q 165. What is the difference between application and cache variables?

Q 166. What is the difference between control and component?

Q 167. You ve defined one page_load event in aspx page and same page_load event in code behind how will prog run?

Q 168. Where would you use an IHttpModule, and what are the limitations of any approach you might take in implementing one?

Ans:- Can you edit data in the Repeater control? Which template must you provide, in order to display data in a Repeater control? How can you provide an alternating color scheme in a Repeater control? What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?

Q 169. What is the use of web.config? Difference between machine.config and Web.config?

Ans :- ASP.NET configuration files are XML-based text files--each named web.config--that can appear in any directory on an ASP.NET Web application server. Each web.config file applies configuration settings to the directory it is located in and to all virtual child directories beneath it. Settings in child directories can optionally override or modify settings specified in parent directories. The root configuration file--WinNT\Microsoft.NET\Framework\<version>\config\machine.config--provides default configuration settings for the entire machine. ASP.NET configures IIS to prevent direct browser access to web.config


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files to ensure that their values cannot become public (attempts to access them will cause ASP.NET to return 403: Access Forbidden). At run time ASP.NET uses these web.config configuration files to hierarchically compute a unique collection of settings for each incoming URL target request (these settings are calculated only once and then cached across subsequent requests; ASP.NET automatically watches for file changes and will invalidate the cache if any of the configuration files change). http://samples.gotdotnet.com/quickstart/aspplus/doc/configformat.aspx

Q 170. What is the use of sessionstate tag in the web.config file?

Ans :- Configuring session state: Session state features can be configured via the <sessionState> section in a web.config file. To double the default timeout of 20 minutes, you can add the following to the web.config file of an application: <sessionState timeout="40" />

Q 171. What are the different modes for the sessionstates in the web.config file?

Ans :-

Off Indicates that session state is not enabled. Inproc Indicates that session state is stored

locally. StateServer Indicates that session state is stored on a

remote server. SQLServer Indicates that session state is stored on the

SQL Server. Q 172. What is smart navigation?

Ans :- When a page is requested by an Internet Explorer 5 browser, or later, smart navigation enhances the user's experience of the page by performing the following:

eliminating the flash caused by navigation.


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persisting the scroll position when moving from page to page.

persisting element focus between navigations.

retaining only the last page state in the browser's history. Smart navigation is best used with ASP.NET pages that require frequent postbacks but with visual content that does not change dramatically on return. Consider this carefully when deciding whether to set this property to true. Set the SmartNavigation attribute to true in the @ Page directive in the .aspx file. When the page is requested, the dynamically generated class sets this property. Q 173. In what order do the events of an ASPX page execute. As a

developer is it important to undertsand these events?

Q 174. How would you get ASP.NET running in Apache web servers - why would you even do this?

Q 175. What tags do you need to add within the asp:datagrid tags to bind columns manually

Q 176. What base class do all Web Forms inherit from?

Ans :- System.Web.UI.Page

Q 177. How can we create pie chart in asp.net?

Q 178. Is it possible for me to change my aspx file extension to some other name?

Ans :-Yes. Open IIS->Default Website -> Properties Select HomeDirectory tab Click on configuration button Click on add. Enter aspnet_isapi details (C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\aspnet_isapi.dll | GET,HEAD,POST,DEBUG) Open machine.config(C:\WINDOWS\Microsoft.NET\Framework\v1.0.3705\C


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ONFIG) & add new extension under <httpHandlers> tag <add verb="*" path="*.santhosh" type="System.Web.UI.PageHandlerFactory"/>

Q 179. What is AutoEventWireup attribute for ? (WEBSERVICE & REMOTING)

Q 180. What is a WebService and what is the underlying protocol used in it?Why Web Services?

Ans :- Web Services are applications delivered as a service on the Web. Web services allow for programmatic access of business logic over the Web. Web services typically rely on XML-based protocols, messages, and interface descriptions for communication and access. Web services are designed to be used by other programs or applications rather than directly by end user. Programs invoking a Web service are called clients. SOAP over HTTP is the most commonly used protocol for invoking Web services. There are three main uses of Web services.

Application integration Web services within an intranet are commonly used to integrate business applications running on disparate platforms. For example, a .NET client running on Windows 2000 can easily invoke a Java Web service running on a mainframe or Unix machine to retrieve data from a legacy application.

Business integration Web services allow trading partners to engage in e-business leveraging the existing Internet infrastructure. Organizations can send electronic purchase orders to suppliers and receive electronic invoices. Doing e-business with Web services means a low barrier to entry because Web services can be added to existing applications running on any platform without changing legacy code.

Commercial Web services focus on selling content and business services to clients over the Internet similar to familiar Web pages. Unlike Web pages, commercial Web services target applications not humans as their direct users. Continental Airlines exposes flight schedules and status Web services for travel Web sites and agencies to use in their applications.


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Like Web pages, commercial Web services are valuable only if they expose a valuable service or content. It would be very difficult to get customers to pay you for using a Web service that creates business charts with the customers? data. Customers would rather buy a charting component (e.g. COM or .NET component) and install it on the same machine as their application. On the other hand, it makes sense to sell real-time weather information or stock quotes as a Web service. Technology can help you add value to your services and explore new markets, but ultimately customers pay for contents and/or business services, not for technology

Q 181. Are Web Services a replacement for other distributed computing platforms?

Ans:- No. Web Services is just a new way of looking at existing implementation platforms.

Q 182. In a Webservice, need to display 10 rows from a table. So DataReader or DataSet is best choice?

Ans:- WebService will support only DataSet.

Q 183. How to generate WebService proxy? What is SOAP, WSDL, UDDI and the concept behind Web Services? What are various components of WSDL? What is the use of WSDL.exe utility?

Ans :- SOAP is an XML-based messaging framework specifically designed for exchanging formatted data across the Internet, for example using request and reply messages or sending entire documents. SOAP is simple, easy to use, and completely neutral with respect to operating system, programming language, or distributed computing platform. After SOAP became available as a mechanism for exchanging XML messages among enterprises (or among disparate applications within the same enterprise), a better way was needed to describe the messages and how they are exchanged. The Web Services Description Language (WSDL) is a particular form of an XML Schema, developed by Microsoft and IBM for the purpose of defining the XML message, operation, and protocol mapping of a web service accessed using SOAP or other XML protocol. WSDL defines web services in terms of "endpoints" that operate on XML messages. The WSDL syntax allows both the messages and the operations on the messages to be defined abstractly, so they can be mapped to multiple physical implementations. The current WSDL spec describes


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how to map messages and operations to SOAP 1.1, HTTP GET/POST, and MIME. WSDL creates web service definitions by mapping a group of endpoints into a logical sequence of operations on XML messages. The same XML message can be mapped to multiple operations (or services) and bound to one or more communications protocols (using "ports"). The Universal Description, Discovery, and Integration (UDDI) framework defines a data model (in XML) and SOAP APIs for registration and searches on business information, including the web services a business exposes to the Internet. UDDI is an independent consortium of vendors, founded by Microsoft, IBM, and Ariba, for the purpose of developing an Internet standard for web service description registration and discovery. Microsoft, IBM, and Ariba also are hosting the initial deployment of a UDDI service, which is conceptually patterned after DNS (the Internet service that translates URLs into TCP addresses). UDDI uses a private agreement profile of SOAP (i.e. UDDI doesn't use the SOAP serialization format because it's not well suited to passing complete XML documents (it's aimed at RPC style interactions). The main idea is that businesses use the SOAP APIs to register themselves with UDDI, and other businesses search UDDI when they want to discover a trading partner, for example someone from whom they wish to procure sheet metal, bolts, or transistors. The information in UDDI is categorized according to industry type and geographical location, allowing UDDI consumers to search through lists of potentially matching businesses to find the specific one they want to contact. Once a specific business is chosen, another call to UDDI is made to obtain the specific contact information for that business. The contact information includes a pointer to the target business's WSDL or other XML schema file describing the web service that the target business publishes.

Q 184. How to generate proxy class other than .net app and wsdl tool?

Ans :- To access an XML Web service from a client application, you first add a Web reference, which is a reference to an XML Web service. When you create a Web reference, Visual Studio creates an XML Web service proxy class automatically and adds it to your project. This proxy class exposes the methods of the XML Web service and handles the marshalling of appropriate arguments back and forth between the XML Web service and your application. Visual Studio uses the Web Services


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Description Language (WSDL) to create the proxy. To generate an XML Web service proxy class:

From a command prompt, use Wsdl.exe to create a proxy class, specifying (at a minimum) the URL to an XML Web service or a service description, or the path to a saved service description. Wsdl /language:language /protocol:protocol /namespace:myNameSpace /out:filename /username:username /password:password /domain:domain <url or path>

Q 185. What is a proxy in web service? How do I use a proxy server when invoking a Web service?

Q 186. asynchronous web service means?

Q 187. What are the events fired when web service called?

Q 188. How will do transaction in Web Services?

Q 189. How does SOAP transport happen and what is the role of HTTP in it? How you can access a webservice using soap?

Q 190. What are the different formatters can be used in both? Why?.. binary/soap?

Q 191. How you will protect / secure a web service?

Ans :- For the most part, things that you do to secure a Web site can be used to secure a Web Service. If you need to encrypt the data exchange, you use Secure Sockets Layer (SSL) or a Virtual Private Network to keep the bits secure. For authentication, use HTTP Basic or Digest authentication with Microsoft® Windows® integration to figure out who the caller is. these items cannot:

Parse a SOAP request for valid values

Authenticate access at the Web Method level (they can authenticate at the Web Service level)

Stop reading a request as soon as it is recognized as invalid


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http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcontransactionsupportinaspnetwebservices.asp Q 192. How will you expose/publish a webservice?

Q 193. What is disco file?

Q 194. What�s the attribute for webservice method? What is the namespace for creating webservice?

Ans :- [WebMethod] using System.Web; using System.Web.Services;

Q 195. What is Remoting?

Ans :- The process of communication between different operating system processes, regardless of whether they are on the same computer. The .NET remoting system is an architecture designed to simplify communication between objects living in different application domains, whether on the same computer or not, and between different contexts, whether in the same application domain or not.

Q 196. Difference between web services & remoting?

Ans :-

ASP.NET Web Services

.NET Remoting

Protocol Can be accessed only over HTTP

Can be accessed over any protocol (including TCP, HTTP, SMTP and so on)

State Management

Web services work in a stateless environment

Provide support for both stateful and stateless


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environments through Singleton and SingleCall objects

Type System

Web services support only the datatypes defined in the XSD type system, limiting the number of objects that can be serialized.

Using binary communication, .NET Remoting can provide support for rich type system

Interoperability

Web services support interoperability across platforms, and are ideal for heterogeneous environments.

.NET remoting requires the client be built using .NET, enforcing homogenous environment.

Reliability

Highly reliable due to the fact that Web services are always hosted inIIS

Can also take advantage of IIS for fault isolation. If IIS is not used, application needs to provide plumbing for ensuring the reliability of


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the application.

Extensibility

Provides extensibility by allowing us to intercept the SOAP messages during the serialization and deserialization stages.

Very extensible by allowing us to customize the different components of the .NET remoting framework.

Ease-of-Programming

Easy-to-create and deploy.

Complex to program.

Though both the .NET Remoting infrastructure and ASP.NET Web services can enable cross-process communication, each is designed to benefit a different target audience. ASP.NET Web services provide a simple programming model and a wide reach. .NET Remoting provides a more complex programming model and has a much narrower reach. As explained before, the clear performance advantage provided by TCPChannel-remoting should make you think about using this channel whenever you can afford to do so. If you can create direct TCP connections from your clients to your server and if you need to support only the .NET platform, you should go for this channel. If you are going to go cross-platform or you have the requirement of supporting SOAP via HTTP, you should definitely go for ASP.NET Web services. Both the .NET remoting and ASP.NET Web services are powerful technologies that provide a suitable framework for developing distributed applications. It is important to understand how both technologies work and then choose the one that is right for your application. For applications that require interoperability and must function over public networks, Web services are probably the best bet. For those that require communications with other .NET components and where performance is a key priority, .NET Remoting is the best choice. In short, use Web services when you need to send and receive data from different computing platforms, use .NET Remoting when sending and receiving data between


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.NET applications. In some architectural scenarios, you might also be able to use.NET Remoting in conjunction with ASP.NET Web services and take advantage of the best of both worlds. The Key difference between ASP.NET webservices and .NET Remoting is how they serialize data into messages and the format they choose for metadata. ASP.NET uses XML serializer for serializing or Marshalling. And XSD is used for Metadata. .NET Remoting relies on System.Runtime.Serialization.Formatter.Binary and System.Runtime.Serialization.SOAPFormatter and relies on .NET CLR Runtime assemblies for metadata.

Q 197. Can you pass SOAP messages through remoting?CAO and SAO.?

Ans :- Client Activated objects are those remote objects whose Lifetime is directly Controlled by the client. This is in direct contrast to SAO. Where the server, not the client has complete control over the lifetime of the objects. Client activated objects are instantiated on the server as soon as the client request the object to be created. Unlike as SAO a CAO doesn�t delay the object creation until the first method is called on the object. (In SAO the object is instantiated when the client calls the method on the object)

singleton and singlecall. Singleton types never have more than one instance at any one time. If an instance exists, all client requests are serviced by that instance. Single Call types always have one instance per client request. The next method invocation will be serviced by a different server instance, even if the previous instance has not yet been recycled by the system.

Q 198. What is Asynchronous Web Services?

Q 199. Web Client class and its methods?

Q 200. Flow of remoting?

Q 201. What is the use of trace utility? Using the SOAP Trace Utility?


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Ans :- The Microsoft® Simple Object Access Protocol (SOAP) Toolkit 2.0 includes a TCP/IP trace utility, MSSOAPT.EXE. You use this trace utility to view the SOAP messages sent by HTTP between a SOAP client and a service on the server.

Using the Trace Utility on the Server To see all of a service's messages received from and sent to all clients, perform the following steps on the server.

On the server, open the Web Services Description Language (WSDL) file.

In the WSDL file, locate the <soap:address> element that corresponds to the service and change the location attribute for this element to port 8080. For example, if the location attribute specifies <http://MyServer/VDir/Service.wsdl> change this attribute to <http://MyServer:8080/VDir/Service.wsdl>.

Run MSSOAPT.exe.

On the File menu, point to New, and either click Formatted Trace (if you don't want to see HTTP headers) or click Unformatted Trace (if you do want to see HTTP headers).

In the Trace Setup dialog box, click OK to accept the default values.

Using the Trace Utility on the Client To see all messages sent to and received from a service, do the following steps on the client.

Copy the WSDL file from the server to the client.

Modify location attribute of the <soap:address> element in thelocal copy of the WSDL document to direct the client to localhost:8080 and make a note of the current host and port. For example, if the WSDL contains <http://MyServer/VDir/Service.wsdl>, change it to <http://localhost:8080/VDir/Service.wsdl> and make note of "MyServer".

On the client, run MSSOPT.exe.

On the File menu, point to New, and either click Formatted Trace (if you don't want to see HTTP headers) or click Unformatted Trace (if you do want to see HTTP headers).


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In the Destination host box, enter the host specified in Step 2.

In the Destination port box, enter the port specified in Step 2.

Click OK.

(XML) Q 202. Explain the concept of data island?

Q 203. How to use XML DOM model on client side using JavaScript.

Q 204. What are the ways to create a tree view control using XML, XSL & JavaScript?

Q 205. Questions on XPathNavigator, and the other classes in System.XML Namespace?

Q 206. What is Use of Template in XSL?

Q 207. What is �Well Formed XML� and �Valid XML�

Q 208. How you will do SubString in XSL

Q 209. Can we do sorting in XSL ? how do you deal sorting columns dynamically in XML?

Q 210. What is �Async� property of XML Means ?

Q 211. What is XPath Query ?

Q 212. Difference Between Element and Node.

Q 213. What is CDATA Section.

Q 214. DOM & SAX parsers explanation and difference

Q 215. What is GetElementbyname method will do?

Q 216. What is selectnode method will give?

Q 217. What is valid xml document? What a well formed xml document?


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Q 218. What is the Difference between XmlDocument and XmlDataDocument?

Q 219. Explain what a DiffGram is, and a good use for one?

Ans :- A DiffGram is an XML format that is used to identify current and original versions of data elements. When sending and retrieving a DataSet from an XML Web service, the DiffGram format is implicitly used. The DataSet uses the DiffGram format to load and persist its contents, and to serialize its contents for transport across a network connection. When a DataSet is written as a DiffGram, it populates the DiffGram with all the necessary information to accurately recreate the contents, though not the schema, of the DataSet, including column values from both the Original and Current row versions, row error information, and row order. DiffGram Format The DiffGram format is divided into three sections: the current data, the original (or "before") data, and an errors section, as shown in the following example.

<?xml version="1.0"?> <diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <DataInstance> </DataInstance> <diffgr:before> </diffgr:before> <diffgr:errors> </diffgr:errors> </diffgr:diffgram>

The DiffGram format consists of the following blocks of data: <DataInstance>


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The name of this element, DataInstance, is used for explanation purposes in this documentation. A DataInstance element represents a DataSet or a row of a DataTable. Instead of DataInstance, the element would contain the name of the DataSet or DataTable. This block of the DiffGram format contains the current data, whether it has been modified or not. An element, or row, that has been modified is identified with the diffgr:hasChanges annotation. <diffgr:before> This block of the DiffGram format contains the original version of a row. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation. <diffgr:errors> This block of the DiffGram format contains error information for a particular row in the DataInstance block. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation. Q 220. If I replace my Sqlserver with XML files and how about

handling the same?

Q 221. Write syntax to serialize class using XML Serializer? (IIS)

Q 222. In which process does IIS runs (was asking about the EXE file)

Ans:- inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.

Q 223. Where are the IIS log files stored?


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Ans :- C:\WINDOWS\system32\Logfiles\W3SVC1 OR c:\winnt\system32\LogFiles\W3SVC1

Q 224. What are the different IIS authentication modes in IIS 5.0 and Explain? Difference between basic and digest authentication modes?

Ans:- IIS provides a variety of authentication schemes:

Anonymous (enabled by default)

Basic

Digest

Integrated Windows authentication (enabled by default)

Client Certificate Mapping Anonymous Anonymous authentication gives users access to the public areas of your Web site without prompting them for a user name or password. Although listed as an authentication scheme, it is not technically performing any client authentication because the client is not required to supply any credentials. Instead, IIS provides stored credentials to Windows using a special user account, IUSR_machinename. By default, IIS controls the password for this account. Whether or not IIS controls the password affects the permissions the anonymous user has. When IIS controls the password, a sub authentication DLL (iissuba.dll) authenticates the user using a network logon. The function of this DLL is to validate the password supplied by IIS and to inform Windows that the password is valid, thereby authenticating the client. However, it does not actually provide a password to Windows. When IIS does not control the password, IIS calls the LogonUser() API in Windows and provides the account name, password and domain name to log on the user using a local logon. After the logon, IIS caches the security token and impersonates the account. A local logon makes it possible for the anonymous user to access network resources, whereas a network logon does not. Basic Authentication IIS Basic authentication as an implementation of the basic authentication scheme found in section 11 of the HTTP 1.0 specification. As the specification makes clear, this method is, in and of itself, non-


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secure. The reason is that Basic authentication assumes a trusted connection between client and server. Thus, the username and password are transmitted in clear text. More specifically, they are transmitted using Base64 encoding, which is trivially easy to decode. This makes Basic authentication the wrong choice to use over a public network on its own. Basic Authentication is a long-standing standard supported by nearly all browsers. It also imposes no special requirements on the server side -- users can authenticate against any NT domain, or even against accounts on the local machine. With SSL to shelter the security credentials while they are in transmission, you have an authentication solution that is both highly secure and quite flexible. Digest Authentication The Digest authentication option was added in Windows 2000 and IIS 5.0. Like Basic authentication, this is an implementation of a technique suggested by Web standards, namely RFC 2069 (superceded by RFC 2617). Digest authentication also uses a challenge/response model, but it is much more secure than Basic authentication (when used without SSL). It achieves this greater security not by encrypting the secret (the password) before sending it, but rather by following a different design pattern -- one that does not require the client to transmit the password over the wire at all. Instead of sending the password itself, the client transmits a one-way message digest (a checksum) of the user's password, using (by default) the MD5 algorithm. The server then fetches the password for that user from a Windows 2000 Domain Controller, reruns the checksum algorithm on it, and compares the two digests. If they match, the server knows that the client knows the correct password, even though the password itself was never sent. (If you have ever wondered what the default ISAPI filter "md5filt" that is installed with IIS 5.0 is used for, now you know. Integrated Windows Authentication Integrated Windows authentication (formerly known as NTLM authentication and Windows NT Challenge/Response authentication) can use either NTLM or Kerberos V5 authentication and only works with Internet Explorer 2.0 and later. When Internet Explorer attempts to access a protected resource, IIS sends two WWW-Authenticate headers, Negotiate and NTLM. If Internet Explorer recognizes the Negotiate header, it will choose it because it is listed first. When using Negotiate, the browser will return


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information for both NTLM and Kerberos. At the server, IIS will use Kerberos if both the client (Internet Explorer 5.0 and later) and server (IIS 5.0 and later) are running Windows 2000 and later, and both are members of the same domain or trusted domains. Otherwise, the server will default to using NTLM.

If Internet Explorer does not understand Negotiate, it will use NTLM. So, which mechanism is used depends upon a negotiation between Internet Explorer and IIS. When used in conjunction with Kerberos v5 authentication, IIS can delegate security credentials among computers running Windows 2000 and later that are trusted and configured for delegation. Delegation enables remote access of resources on behalf of the delegated user. Integrated Windows authentication is the best authentication scheme in an intranet environment where users have Windows domain accounts, especially when using Kerberos. Integrated Windows authentication, like digest authentication, does not pass the user's password across the network. Instead, a hashed value is exchanged. Client Certificate Mapping A certificate is a digitally signed statement that contains information about an entity and the entity's public key, thus binding these two pieces of information together. A trusted organization (or entity) called a Certification Authority (CA) issues a certificate after the CA verifies that the entity is who it says it is. Certificates can contain different types of data. For example, an X.509 certificate includes the format of the certificate, the serial number of the certificate, the algorithm used to sign the certificate, the name of the CA that issued the certificate, the name and public key of the entity requesting the certificate, and the CA's signature. X.509 client certificates simplify authentication for larger user bases because they do not rely on a centralized account database. You can verify a certificate simply by examining the certificate. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsent7/html/vxconIISAuthentication.asp Q 225. How to configure the sites in Web server (IIS)? Advantages in

IIS 6.0?

Ans :- http://www.microsoft.com/windowsserver2003/iis/evaluation/features/default.mspx


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http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/windowsserver2003/proddocs/datacenter/gs_whatschanged.asp

Q 226. IIS Isolation Levels?

Ans:- Internet Information Server introduced the notion "Isolation Level", which is also present in IIS4 under a different name. IIS5 supports three isolation levels, that you can set from the Home Directory tab of the site's Properties dialog:

Low (IIS Process): ASP pages run in INetInfo.Exe, the main IIS process, therefore they are executed in-process. This is the fastest setting, and is the default under IIS4. The problem is that if ASP crashes, IIS crashes as well and must be restarted (IIS5 has a reliable restart feature that automatically restarts a server when a fatal error occurs).

Medium (Pooled): In this case ASP runs in a different process, which makes this setting more reliable: if ASP crashes IIS won't. All the ASP applications at the Medium isolation level share the same process, so you can have a web site running with just two processes (IIS and ASP process). IIS5 is the first Internet Information Server version that supports this setting, which is also the default setting when you create an IIS5 application. Note that an ASP application that runs at this level is run under COM+, so it's hosted in DLLHOST.EXE (and you can see this executable in the Task Manager).

High (Isolated): Each ASP application runs out-process in its own process space, therefore if an ASP application crashes, neither IIS nor any other ASP application will be affected. The downside is that you consume more memory and resources if the server hosts many ASP applications. Both IIS4 and IIS5 supports this setting: under IIS4 this process runs inside MTS.EXE, while under IIS5 it runs inside DLLHOST.EXE. When selecting an isolation level for your ASP application, keep in mind that out-process settings - that is, Medium and High - are less efficient than in-process (Low). However, out-process communication has been vastly improved under IIS5, and in fact IIS5's Medium isolation level often deliver better results than IIS4's Low isolation. In practice, you shouldn't set the Low isolation level for an IIS5 application unless you really need to serve hundreds pages per second.


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Controls Q 227. How will you do Redo and Undo in a TextControl?

Q 228. How to implement DataGrid in .NET?

Q 229. How would u make a combo-box appear in one column of a DataGrid?

Q 230. What are the ways to show data grid inside a data grid for a master details type of tables? If we write any code for DataGrid methods, what is the access specifier used for that methods in the code behind file and why?

Q 231. How can we create Tree control in asp.net? Programming

Q 232. Write a program in C# for checking a given number is PRIME or not.

Q 233. Write a program to find the angle between the hours and minutes in a clock

Q 234. Write a C# program to find the Factorial of n

Q 235. How do I upload a file from my ASP.NET page?

Ans :- In order to perform file upload in your ASP.NET page, you will need to use two classes: the System.Web.UI.HtmlControls.HtmlInputFile class and the System.Web.HttpPostedFile class. The HtmlInputFile class represents and HTML input control that the user will use on the client side to select a file to upload. The HttpPostedFile class represents the uploaded file and is obtained from the PostedFile property of the HtmlInputFile class. In order to use the HtmlInputFile control, you need to add the enctype attribute to your form tag as follows: <form id="upload" method="post" runat="server" enctype="multipart/form-data">


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Also, remember that the /data directory is the only directory with Write permissions enabled for the anonymous user. Therefore, you will need to make sure that the your code uploads the file to the /data directory or one of its subdirectories. Below is a simple example of how to upload a file via an ASP.NET page in C# and VB.NET. C# <%@ Import Namespace="System" %> <%@ Import Namespace="System.Web" %> <%@ Import Namespace="System.Web.UI.HtmlControls" %> <%@ Import Namespace="System.IO" %> <%@ Import Namespace="System.Drawing" %> <html> <head> <title>upload_cs</title> </head> <script language="C#" runat="server"> public void UploadFile(object sender, EventArgs e) { if (loFile.PostedFile != null) { try { string strFileName, strFileNamePath, strFileFolder; strFileFolder = Context.Server.MapPath(@"data\"); strFileName = loFile.PostedFile.FileName; strFileName = Path.GetFileName(strFileName); strFileNamePath = strFileFolder + strFileName; loFile.PostedFile.SaveAs(strFileNamePath); lblFileName.Text = strFileName; lblFileLength.Text = loFile.PostedFile.ContentLength.ToString(); lblFileType.Text = loFile.PostedFile.ContentType; pnStatus.Visible = true; } catch (Exception x) { Label lblError = new Label(); lblError.ForeColor = Color.Red; lblError.Text = "Exception occurred: " + x.Message; lblError.Visible = true;


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this.Controls.Add(lblError); } } } </script> <body> <form id="upload_cs" method="post" runat="server" enctype="multipart/form-data"> <P> <INPUT type="file" id="loFile" runat="server"> </P> <P> <asp:Button id="btnUpload" runat="server" Text=" Upload " OnClick="UploadFile"></asp:Button></P> <P> <asp:Panel id="pnStatus" runat="server" Visible="False"> <asp:Label id="lblFileName" Font-Bold="True" Runat="server"></asp:Label> uploaded<BR> <asp:Label id="lblFileLength" Runat="server"></asp:Label> bytes<BR> <asp:Label id="lblFileType" Runat="server"></asp:Label> </asp:Panel></P> </form> </body> </html>

Q 236. How do I send an email message from my ASP.NET page?

Ans :- You can use the System.Web.Mail.MailMessage and the System.Web.Mail.SmtpMail class to send email in your ASPX pages. Below is a simple example of using this class to send mail in C# and VB.NET. In order to send mail through our mail server, you would want to make sure to set the static SmtpServer property of the SmtpMail class to mail-fwd. C# <%@ Import Namespace="System" %> <%@ Import Namespace="System.Web" %> <%@ Import Namespace="System.Web.Mail" %> <HTML> <HEAD>


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<title>Mail Test</title> </HEAD> <script language="C#" runat="server"> private void Page_Load(Object sender, EventArgs e) { try { MailMessage mailObj = new MailMessage(); mailObj.From = "[email protected]"; mailObj.To = "[email protected]"; mailObj.Subject = "Your Widget Order"; mailObj.Body = "Your order was processed."; mailObj.BodyFormat = MailFormat.Text; SmtpMail.SmtpServer = "mail-fwd"; SmtpMail.Send(mailObj); Response.Write("Mail sent successfully"); } catch (Exception x) { Response.Write("Your message was not sent: " + x.Message); } } </script> <body> <form id="mail_test" method="post" runat="server"> </form> </body> </HTML>

Q 237. Write a program to create a user control with name and surname as data members and login as method and also the code to call it. (Hint use event delegates) Practical Example of Passing an Events to delegates ?

Q 238. How can you read 3rd line from a text file?

Q 239. Can I do things in IL that I can't do in C#?


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Ans :- Yes. A couple of simple examples are that you can throw exceptions that are not derived from System.Exception, and you can have non-zero-based arrays.

1. DOT NET

1.1 What is .NET? Ans :- .NET is a �revolutionary new platform, built on open Internet protocols and standards, with tools and services that meld computing and communications in new ways�. A more practical definition would be that .NET is a new environment for developing and running software applications, featuring ease of development of web-based services, rich standard run-time services available to components written in a variety of programming languages, and inter-language and inter-machine interoperability.

1.2 Does .NET only apply to people building web-sites? Ans :- No. If you write any Windows software (using ATL/COM, MFC, VB, or even raw Win32), .NET may offer a viable alternative (or addition) to the way you do things currently. Of course, if you do develop web sites, then .NET has lots to interest you � not least ASP.NET.


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1.3 What platforms does the .NET Framework run on? Ans :- The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms � for example, ASP.NET is only supported on Windows XP and Windows 2000. Windows 98/ME cannot be used for development. IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix web server does run on XP Home. The Mono project is attempting to implement the .NET framework on Linux.

1.4 What languages does the .NET Framework support? Asn :- MS provides compilers for C#, C++, VB and Jscript. Other vendors have announced that they intend to develop .NET compilers for languages such as COBOL, Eiffel, Perl, Smalltalk and Python.

1.5 Will the .NET Framework go through a !tandardization process? Asn :- From http://msdn.microsoft.com/net/ecma/: �On December 13, 2001, the ECMA General Assembly ratified the C# and common language infrastructure (CLI) specifications into international standards. The ECMA standards will be known as ECMA-334 (C#) and ECMA-335 (the CLI).�

2. Basic terminology

2.1 What is the CLR? Ans:- CLR = Common Language Runtime. The CLR is a set of standard resources that (in theory) any .NET program can take advantage of, regardless of programming language. • Object-oriented programming model (inheritance, polymorphism,

exception handling, garbage collection) • Security model • Type system • All .NET base classes • Many .NET framework classes


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• Development, debugging, and profiling tools • Execution and code management • IL-to-native translators and optimizers What this means is that in the .NET world, different programming languages will be more equal in capability than they have ever been before, although clearly not all languages will support all CLR services.

2.2 What is the CTS? Ans :- CTS = Common Type System. This is the range of types that the .NET runtime understands, and therefore that .NET applications can use. However note that not all .NET languages will support all the types in the CTS. The CTS is a superset of the CLS.

2.3 What is the CLS? Ans :- CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language. In theory this allows very tight interop between different .NET languages � for example allowing a C# class to inherit from a VB class.

2.4 What is IL? Ans:- IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code (of any language) is compiled to IL. The IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In-Time (JIT) compiler.

2.5 What is C#? Ans:- C# is a new language designed by Microsoft to work with the .NET framework. �C# is a simple, modern, object oriented, and type-safe programming language derived from C and C++. C# (pronounced �C sharp�) is firmly planted in the C and C++ family tree of languages, and will immediately be familiar to C and C++ programmers. C# aims to combine the high productivity of Visual Basic and the raw power of C++.�


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Substitute �Java� for �C#� in the quote above, and you�ll see that the statement still works pretty well ☺.

2.6 What does �managed� mean in the .NET context? Ans :- The term �managed� is the cause of much confusion. It is used in various places within .NET, meaning slightly different things. Managed code: The .NET framework provides several core run-time services to the programs that run within it � for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. Such code is called managed code. All C# and Visual Basic.NET code is managed by default. VS7 C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/com+). Managed data: This is data that is allocated and de-allocated by the .NET runtime�s garbage collector. C# and VB.NET data is always managed. VS7 C++ data is unmanaged by default, even when using the /com+ switch, but it can be marked as managed using the __gc keyword. Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages � for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class.

2.7 What is reflection? Ans :- All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly. Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used


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for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries. Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember), or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder).

3. Assemblies

3.1 What is an assembly? Ans :- An assembly is sometimes described as a logical .EXE or .DLL, and can be an application (with a main entry point) or a library. An assembly consists of one or more files (dlls, exes, html files etc), and represents a group of resources, type definitions, and implementations of those types. An assembly may also contain references to other assemblies. These resources, types and references are described in a block of data called a manifest. The manifest is part of the assembly, thus making the assembly self-describing. An important aspect of assemblies is that they are part of the identity of a type. The identity of a type is the assembly that houses it combined with the type name. This means, for example, that if assembly A exports a type called T, and assembly B exports a type called T, the .NET runtime sees these as two completely different types. Furthermore, don�t get confused between assemblies and namespaces � namespaces are merely a hierarchical way of !rganize!g type names. To the runtime, type names are type names, regardless of whether namespaces are used to !rganize the names. It�s the assembly plus the type name (regardless of whether the type name belongs to a namespace) that uniquely identifies a type to the runtime. Assemblies are also important in .NET with respect to security � many of the security restrictions are enforced at the assembly boundary. Finally, assemblies are the unit of versioning in .NET.

3.2 How can I produce an assembly? Ans :- The simplest way to produce an assembly is directly from a .NET compiler. For example, the following C# program: Public class CTest {


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Public CTest () { System.Console.WriteLine ("Hello from CTest"); } } Can be compiled into a library assembly (dll) like this: csc /t:library ctest.cs You can then view the contents of the assembly by running the "IL Disassembler" tool that comes with the .NET SDK. Alternatively you can compile your source into modules, and then combine the modules into an assembly using the assembly linker (al.exe). For the C# compiler, the /target:module switch is used to generate a module instead of an assembly.

3.3 What is the difference between a private assembly and a shared assembly? Ans :- Location and visibility: A private assembly is normally used by a single application, and is stored in the application�s directory, or a sub-directory beneath. A shared assembly is normally stored in the global assembly cache, which is a repository of assemblies maintained by the .NET runtime. Shared assemblies are usually libraries of code which many applications will find useful, e.g. the .NET framework classes. • Versioning: The runtime enforces versioning constraints only on

shared assemblies, not on private assemblies.

3.4 How do assemblies find each other? Ans :- By searching directory paths. There are several factors, which can affect the path (such as the AppDomain host, and application configuration files), but for private assemblies the search path is normally the application�s directory and its sub-directories. For shared assemblies, the search path is normally same as the private assembly path plus the shared assembly cache.

3.5 How does assembly versioning work? Ans :- Each assembly has a version number called the compatibility version. Also each reference to an assembly (from another assembly) includes both the name and version of the referenced assembly.


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The version number has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the first two parts different are normally viewed as incompatible. If the first two parts are the same, but the third is different, the assemblies are deemed as 'maybe compatible'. If only the fourth part is different, the assemblies are deemed compatible. However, this is just the default guideline - it is the version policy that decides to what extent these rules are enforced. The version policy can be specified via the application configuration file. Remember: versioning is only applied to shared assemblies, not private assemblies.

4. Application Domains

4.1 What is an Application Domain? Ans :- An AppDomain can be thought of as a lightweight process. Multiple AppDomains can exist inside a Win32 process. The primary purpose of the AppDomain is to isolate an application from other applications. Win32 processes provide isolation by having distinct memory address spaces. This is effective, but it is expensive and doesn�t scale well. The .NET runtime enforces AppDomain isolation by keeping control over the use of memory � all memory in the AppDomain is managed by the .NET runtime, so the runtime can ensure that AppDomains do not access each other�s memory.

4.2 How does an AppDomain get created? Ans :- AppDomains are usually created by hosts. Examples of hosts are the Windows Shell, ASP.NET and IE. When you run a .NET application from the command-line, the host is the Shell. The Shell creates a new AppDomain for every application. AppDomains can also be explicitly created by .NET applications. Here is a C# sample which creates an AppDomain, creates an instance of an object inside it, and then executes one of the object's methods. Note that you must name the executable 'appdomaintest.exe' for this code to work as-is. using System;


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using System.Runtime.Remoting; public class CAppDomainInfo : MarshalByRefObject { public string GetAppDomainInfo() { return "AppDomain = " + AppDomain.CurrentDomain.FriendlyName; } } public class App { public static int Main() { AppDomain ad = AppDomain.CreateDomain( "Andy's new domain", null, null ); ObjectHandle oh = ad.CreateInstance( "appdomaintest", "CAppDomainInfo" ); CAppDomainInfo adInfo = (CAppDomainInfo)(oh.Unwrap()); string info = adInfo.GetAppDomainInfo(); Console.WriteLine( "AppDomain info: " + info ); return 0; } }

5. Garbage Collection

5.1 What is garbage collection? Ans :- Garbage collection is a system whereby a run-time component takes responsibility for managing the lifetime of objects and the heap memory that they occupy. This concept is not new to .NET � Java and many other languages/runtimes have used garbage collection for some time.


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5.2 Is it true that objects don�t always get destroyed immediately when the last reference goes away? Ans :- Yes. The garbage collector offers no guarantees about the time when an object will be destroyed and its memory reclaimed.

5.3 Why doesn�t the .NET runtime offer deterministic destruction? Ans :- Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn�t find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn�t get notified immediately when the final reference on an object goes away � it only finds out during the next sweep of the heap. Futhermore, this type of algorithm works best by performing the garbage collection sweep as rarely as possible. Normally heap exhaustion is the trigger for a collection sweep.

5.4 Is the lack of deterministic destruction in .NET a problem? Ans :- It's certainly an issue that affects component design. If you have objects that maintain expensive or scarce resources (e.g. database locks), you need to provide some way for the client to tell the object to release the resource when it is done. Microsoft recommend that you provide a method called Dispose() for this purpose. However, this causes problems for distributed objects - in a distributed system who calls the Dispose() method? Some form of reference-counting or ownership-management mechanism is needed to handle distributed objects - unfortunately the runtime offers no help with this.

5.5 Does non-deterministic destruction affect the usage of COM objects from managed code? Ans :- Yes. When using a COM object from managed code, you are effectively relying on the garbage collector to call the final release on your object. If your COM object holds onto an expensive resource which is only cleaned-up after the final release, you may need to provide a new interface on your object which supports an explicit Dispose() method.


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5.6 I�ve heard that Finalize methods should be avoided. Should I implement Finalize on my class? Ans :- An object with a Finalize method is more work for the garbage collector than an object without one. Also there are no guarantees about the order in which objects are Finalized, so there are issues surrounding access to other objects from the Finalize method. Finally, there is no guarantee that a Finalize method will get called on an object, so it should never be relied upon to do clean-up of an object�s resources. Microsoft recommend the following pattern: public class CTest : Idisposable { public void Dispose() { ... // Cleanup activities GC.SuppressFinalize(this); } ~Ctest() // C# syntax hiding the Finalize() method { Dispose(); } } In the normal case the client calls Dispose(), the object�s resources are freed, and the garbage collector is relieved of its Finalizing duties by the call to SuppressFinalize(). In the worst case, i.e. the client forgets to call Dispose(), there is a reasonable chance that the object�s resources will eventually get freed by the garbage collector calling Finalize(). Given the limitations of the garbage collection algorithm this seems like a pretty reasonable approach.

5.7 Do I have any control over the garbage collection algorithm? Ans :- A little. For example, the System.GC class exposes a Collect method � this forces the garbage collector to collect all unreferenced objects immediately.


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5.8 How can I find out what the garbage collector is doing? Ans :- Lots of interesting statistics are exported from the .NET runtime via the '.NET CLR xxx' performance counters. Use Performance Monitor to view them.

6. Serialization

6.1 What is serialization? Ans :- Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization/Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database).

6.2 Does the .NET Framework have in-built support for serialization? Ans :- There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code.

6.3 I want to serialize instances of my class. Should I use XmlSerializer, SoapFormatter or BinaryFormatter? Ans :- It depends. XmlSerializer has severe limitations such as the requirement that the target class has a parameterless constructor, and only public read/write properties and fields can be serialized. However, on the plus side, XmlSerializer has good support for customising the XML document that is produced or consumed. XmlSerializer's features mean that it is most suitable for cross-platform work, or for constructing objects from existing XML documents. SoapFormatter and BinaryFormatter have fewer limitations than XmlSerializer. They can serialize private fields, for example. However they both require that the target class be marked with the [Serializable] attribute, so like XmlSerializer the class needs to be written with serialization in mind. Also there are some quirks to watch out for - for example on deserialization the constructor of the new object is not invoked.


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The choice between SoapFormatter and BinaryFormatter depends on the application. BinaryFormatter makes sense where both serialization and deserialization will be performed on the .NET platform and where performance is important. SoapFormatter generally makes more sense in all other cases, for ease of debugging if nothing else.

6.4 Can I customise the serialization process? Ans :- Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement] attribute, which can be used to specify the XML element name to be used for a particular property or field. Serialization via SoapFormatter/BinaryFormatter can also be controlled to some extent by attributes. For example, the [NonSerialized] attribute is the equivalent of XmlSerializer�s [XmlIgnore] attribute. Ultimate control of the serialization process can be !chieved by implementing the the Iserializable interface on the class whose instances are to be serialized.

6.5 Why is XmlSerializer so slow? Ans :- There is a once-per-process-per-type overhead with XmlSerializer. So the first time you serialize or deserialize an object of a given type in an application, there is a significant delay. This normally doesn't matter, but it may mean, for example, that XmlSerializer is a poor choice for loading configuration settings during startup of a GUI application.

6.6 Why do I get errors when I try to serialize a Hashtable? Ans :- XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

6.7 XmlSerializer is throwing a generic "There was an error reflecting MyClass" error. How do I find out what the problem is? Ans :- Look at the InnerException property of the exception that is thrown to get a more specific error message.

7. Attributes


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7.1 What are attributes? Ans :- There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute � it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. An example of a metadata attribute is [serializable], which can be attached to a class and means that instances of the class can be serialized. [serializable] public class Ctest {} The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context attributes provide an interception mechanism whereby instance activation and method calls can be pre- and/or post-processed.

7.2 Can I create my own metadata attributes? Ans :- Yes. Simply derive a class from System.Attribute and mark it with the AttributeUsage attribute. For example: [AttributeUsage(AttributeTargets.Class)] public class InspiredByAttribute : System.Attribute { public string InspiredBy; public InspiredByAttribute( string inspiredBy ) { InspiredBy = inspiredBy; } } [InspiredBy("Andy Mc's brilliant .NET FAQ")] class CTest { } class CApp { public static void Main() {


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object[] atts = typeof(CTest).GetCustomAttributes(true); foreach( object att in atts ) if( att is InspiredByAttribute ) Console.WriteLine( "Class CTest was inspired by {0}", ((InspiredByAttribute)att).InspiredBy ); } }

8. Code Access Security

8.1 What is Code Access Security (CAS)? Ans :- CAS is the part of the .NET security model that determines whether or not a piece of code is allowed to run, and what resources it can use when it is running. For example, it is CAS that will prevent a .NET web applet from formatting your hard disk.

8.2 How does CAS work? Ans :- The CAS security policy revolves around two key concepts � code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set. For example, using the default security policy, a control downloaded from a web site belongs to the �Zone � Internet� code group, which adheres to the permissions defined by the �Internet� named permission set. (Naturally the �Internet� named permission set represents a very restrictive range of permissions.)

8.3 Who defines the CAS code groups? Ans :- Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my system it looks like this:


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Level = Machine Code Groups: 1. All code: Nothing 1.1. Zone - MyComputer: FullTrust 1.1.1. Honor SkipVerification requests: SkipVerification 1.2. Zone - Intranet: LocalIntranet 1.3. Zone - Internet: Internet 1.4. Zone - Untrusted: Nothing 1.5. Zone - Trusted: Internet 1.6. StrongName - 0024000004800000940000000602000000240000525341310004000003 000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06 F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08 07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C AC1DF1734633C602F8F2D5: Everything Note the hierarchy of code groups - the top of the hierarchy is the most general ('All code'), which is then sub-divided into several groups, each of which in turn can be sub-divided. Also note that (somewhat counter-intuitively) a sub-group can be associated with a more permissive permission set than its parent.

8.4 How do I define my own code group? Ans :- Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this: caspol -ag 1.3 -site www.mydomain.com FullTrust Now if you run caspol -lg you will see that the new group has been added as group 1.3.1: ... 1.3. Zone - Internet: Internet 1.3.1. Site - www.mydomain.com: FullTrust ...


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Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it.

8.5 How do I change the permission set for a code group? Ans :- Use caspol. If you are the machine administrator, you can operate at the �machine� level � which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this: caspol �cg 1.2 FullTrust Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level � doing it at the user level will have no effect.

8.6 Can I create my own permission set? Ans :- Yes. Use caspol -ap, specifying an XML file containing the permissions in the permission set. When you have created the sample, add it to the range of available permission sets like this: caspol -ap samplepermset.xml Then, to apply the permission set to a code group, do something like this: caspol -cg 1.3 SamplePermSet (By default, 1.3 is the 'Internet' code group)

8.7 I'm having some trouble with CAS. How can I diagnose my problem? Ans :- Caspol has a couple of options that might help. First, you can ask caspol to tell you what code group an assembly belongs to, using caspol �rsg. Similarly, you can ask what permissions are being applied to a particular assembly using caspol �rsp.

8.8 I can�t be bothered with all this CAS stuff. Can I turn it off? Ans :- Yes, as long as you are an administrator. Just run: caspol -s off

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9.1 Can I look at the IL for an assembly? Ans :- Yes. MS supply a tool called Ildasm which can be used to view the metadata and IL for an assembly.

9.2 Can source code be reverse-engineered from IL? Ans :- Yes, it is often relatively straightforward to regenerate high-level source (e.g. C#) from IL.

9.3 How can I stop my code being reverse-engineered from IL? Ans :- There is currently no simple way to stop code being reverse-engineered from IL. In future it is likely that IL obfuscation tools will become available, either from MS or from third parties. These tools work by 'optimising' the IL in such a way that reverse-engineering becomes much more difficult. Of course if you are writing web services then reverse-engineering is not a problem as clients do not have access to your IL.

9.4 Can I write IL programs directly? Ans :- Yes. Simple example .assembly MyAssembly {} .class MyApp { .method static void Main() { .entrypoint ldstr �Hello, IL!� call void System.Console::WriteLine(class System.Object) ret } } Just put this into a file called hello.il, and then run ilasm hello.il. An exe assembly will be generated.

9.5 Can I do things in IL that I can�t do in C#? Ans :- Yes. A couple of simple examples are that you can throw exceptions that are not derived from System.Exception, and you can have non-zero-based arrays.

10. Implications for COM


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10.1 Is COM dead? Ans :- This subject causes a lot of controversy. COM is many things, and it's different things to different people. But to me, COM is fundamentally about how little blobs of code find other little blobs of code, and how they communicate with each other when they find each other. COM specifies precisely how this location and communication takes place. In a 'pure' .NET world, consisting entirely of .NET objects, little blobs of code still find each other and talk to each other, but they don't use COM to do so. They use a model which is similar to COM in some ways - for example, type information is stored in a tabular form packaged with the component, which is quite similar to packaging a type library with a COM component. But it's not COM. So, does this matter? Well, I don't really care about most of the COM stuff going away - I don't care that finding components doesn't involve a trip to the registry, or that I don't use IDL to define my interfaces. But there is one thing that I wouldn't like to go away - I wouldn't like to lose the idea of interface-based development. COM's greatest strength, in my opinion, is its insistence on a cast-iron separation between interface and implementation. Unfortunately, the .NET framework seems to make no such insistence - it lets you do interface-based development, but it doesn't insist. Some people would argue that having a choice can never be a bad thing, and maybe they're right, but I can't help feeling that maybe it's a backward step.

10.2 Is DCOM dead? Ans :- Pretty much, for .NET developers. The .NET Framework has a new remoting model which is not based on DCOM. Of course DCOM will still be used in interop scenarios.

10.3 Is MTS/COM+ dead? Ans :- No. The approach for the first .NET release is to provide access to the existing COM+ services (through an interop layer) rather than replace the services with native .NET ones. Various tools and attributes are provided to try to make this as painless as possible. The PDC release of the .NET SDK includes interop support for core services (JIT activation, transactions) but not some of the higher level services (e.g. COM+ Events, Queued components).


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Over time it is expected that interop will become more seamless � this may mean that some services become a core part of the CLR, and/or it may mean that some services will be rewritten as managed code which runs on top of the CLR.

10.4 Can I use COM components from .NET programs? Ans :- Yes. COM components are accessed from the .NET runtime via a Runtime Callable Wrapper (RCW). This wrapper turns the COM interfaces exposed by the COM component into .NET-compatible interfaces. For oleautomation interfaces, the RCW can be generated automatically from a type library. For non-oleautomation interfaces, it may be necessary to develop a custom RCW which manually maps the types exposed by the COM interface to .NET-compatible types. When you�ve built the COM component, you should get a typelibrary. Run the TLBIMP utility on the typelibary, like this: tlbimp cppcomserver.tlb If successful, you will get a message like this: Typelib imported successfully to CPPCOMSERVERLib.dll You now need a .NET client � let�s use C#. Create a .cs file containing the following code: using System; using CPPCOMSERVERLib; public class MainApp { static public void Main() { CppName cppname = new CppName(); cppname.SetName( �bob� ); Console.WriteLine( �Name is � + cppname.GetName() ); } } Note that we are using the type library name as a namespace, and the COM class name as the class. Alternatively we could have used CPPCOMSERVERLib.CppName for the class name and gone without the using CPPCOMSERVERLib statement. Compile the C# code like this: csc /r:cppcomserverlib.dll csharpcomclient.cs


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Note that the compiler is being told to reference the DLL we previously generated from the typelibrary using TLBIMP. You should now be able to run csharpcomclient.exe, and get the following output on the console: Name is bob

10.5 Can I use .NET components from COM programs? Ans :- Yes. .NET components are accessed from COM via a COM Callable Wrapper (CCW). This is similar to a RCW (see previous question), but works in the opposite direction. Again, if the wrapper cannot be automatically generated by the .NET development tools, or if the automatic behaviour is not desirable, a custom CCW can be developed. Also, for COM to �see� the .NET component, the .NET component must be registered in the registry. Here�s a simple example. Create a C# file called testcomserver.cs and put the following in it: using System; namespace AndyMc { public class CSharpCOMServer { public CSharpCOMServer() {} public void SetName( string name ) { m_name = name; } public string GetName() { return m_name; } private string m_name; } } Then compile the .cs file as follows: csc /target:library testcomserver.cs You should get a dll, which you register like this: regasm testcomserver.dll /tlb:testcomserver.tlb /codebase Now you need to create a client to test your .NET COM component. VBScript will do � put the following in a file called comclient.vbs: Dim dotNetObj Set dotNetObj = CreateObject(�AndyMc.CSharpCOMServer�) dotNetObj.SetName (�bob�) MsgBox �Name is � & dotNetObj.GetName()


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and run the script like this: wscript comclient.vbs And hey presto you should get a message box displayed with the text �Name is bob�.

10.6 Is ATL redundant in the .NET world? Ans :- Yes, if you are writing applications that live inside the .NET framework. Of course many developers may wish to continue using ATL to write C++ COM components that live outside the framework, but if you are inside you will almost certainly want to use C#. Raw C++ (and therefore ATL which is based on it) doesn't have much of a place in the .NET world - it's just too near the metal and provides too much flexibility for the runtime to be able to manage it.

11. Miscellaneous

11.1 How does .NET remoting work? Ans :- .NET remoting involves sending messages along channels. Two of the standard channels are HTTP and TCP. TCP is intended for LANs only � HTTP can be used for LANs or WANs (internet). Support is provided for multiple message serializarion formats. Examples are SOAP (XML-based) and binary. By default, the HTTP channel uses SOAP (via the .NET runtime Serialization SOAP Formatter), and the TCP channel uses binary (via the .NET runtime Serialization Binary Formatter). But either channel can use either serialization format. There are a number of styles of remote access: • SingleCall. Each incoming request from a client is serviced by a

new object. The object is thrown away when the request has finished. This (essentially stateless) model can be made stateful in the ASP.NET environment by using the ASP.NET state service to store application or session state.

• Singleton. All incoming requests from clients are processed by a single server object.


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• Client-activated object. This is the old stateful (D)COM model whereby the client receives a reference to the remote object and holds that reference (thus keeping the remote object alive) until it is finished with it.

Distributed garbage collection of objects is managed by a system called �leased based lifetime�. Each object has a lease time, and when that time expires the object is disconnected from the .NET runtime remoting infrastructure. Objects have a default renew time � the lease is renewed when a successful call is made from the client to the object. The client can also explicitly renew the lease.

11.2 How can I get at the Win32 API from a .NET program? Ans :- Use P/Invoke. This uses similar technology to COM Interop, but is used to access static DLL entry points instead of COM objects. Here is an example of C# calling the Win32 MessageBox function: using System; using System.Runtime.InteropServices; class MainApp { [DllImport("user32.dll", EntryPoint="MessageBox", SetLastError=true, CharSet=CharSet.Auto)] public static extern int MessageBox(int hWnd, String strMessage, String strCaption, uint uiType); public static void Main() { MessageBox( 0, "Hello, this is PInvoke in operation!", ".NET", 0 ); } }

12. Class Library

12.1 File I/O

12.1.1 How do I read from a text file? Ans:- First, use a System.IO.FileStream object to open the file:


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FileStream fs = new FileStream( @"c:\test.txt", FileMode.Open, FileAccess.Read ); FileStream inherits from Stream, so you can wrap the FileStream object with a StreamReader object. This provides a nice interface for processing the stream line by line: StreamReader sr = new StreamReader( fs ); string curLine; while( (curLine = sr.ReadLine()) != null ) Console.WriteLine( curLine ); Finally close the StreamReader object: sr.Close(); Note that this will automatically call Close() on the underlying Stream object, so an explicit fs.Close() is not required.

12.1.2 How do I write to a text file? Ans :- Similar to the read example, except use StreamWriter instead of StreamReader.

12.1.3 How do I read/write binary files? Ans :- Similar to text files, except wrap the FileStream object with a BinaryReader/Writer object instead of a StreamReader/Writer object.

12.1.4 How do I delete a file? Ans :- Use the static Delete() method on the System.IO.File object: File.Delete( @�c:\test.txt� );

12.2 Text Processing

12.2.1 Are regular expressions supported? Ans :- Yes. Use the System.Text.RegularExpressions.Regex class. For example, the following code updates the title in an HTML file: FileStream fs = new FileStream( "test.htm", FileMode.Open, FileAccess.Read ); StreamReader sr = new StreamReader( fs ); Regex r = new Regex( "<TITLE>(.*)</TITLE>" ); string s; while( (s = sr.ReadLine()) != null ) {


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if( r.IsMatch( s ) ) s = r.Replace( s, "<TITLE>New and improved ${1}</TITLE>" ); Console.WriteLine( s ); }

12.3 Internet

12.3.1 How do I download a web page? Ans :- First use the System.Net.WebRequestFactory class to acquire a WebRequest object: WebRequest request = WebRequest.Create( �http://localhost� ); Then ask for the response from the request: WebResponse response = request.GetResponse(); The GetResponse method blocks until the download is complete. Then you can access the response stream like this: Stream s = response.GetResponseStream(); // Output the downloaded stream to the console StreamReader sr = new StreamReader( s ); string line; while( (line = sr.ReadLine()) != null ) Console.WriteLine( line ); Note that WebRequest and WebReponse objects can be downcast to HttpWebRequest and HttpWebReponse objects respectively, to access http-specific functionality.

12.3.2 How do I use a proxy? Ans :- Two approaches � to affect all web requests do this: System.Net.GlobalProxySelection.Select = new WebProxy( �proxyname�, 80 ); Alternatively, to set the proxy for a specific web request, do this: HttpWebRequest request = (HttpWebRequest)WebRequest.Create( �http://localhost� ); request.Proxy = new WebProxy( “proxyname”, 80 );

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12.4.1 Is DOM supported? Ans :- Yes. Take this example XML document: <PEOPLE> <PERSON>Fred</PERSON> <PERSON>Bill</PERSON> </PEOPLE> This document can be parsed as follows: XmlDocument doc = new XmlDocument(); doc.Load( �test.xml� ); XmlNode root = doc.DocumentElement; foreach( XmlNode personElement in root.ChildNodes ) Console.WriteLine( personElement.FirstChild.Value.ToString() ); The output is: Fred Bill

12.4.2 Is SAX supported? Ans :- No. Instead, a new XmlReader/XmlWriter API is offered. Like SAX it is stream-based but it uses a �pull� model rather than SAX�s �push� model. Here�s an example: XmlTextReader reader = new XmlTextReader( �test.xml� ); while( reader.Read() ) { if( reader.NodeType == XmlNodeType.Element && reader.Name == �PERSON� ) { reader.Read(); // Skip to the child text Console.WriteLine( reader.Value ); } }

12.4.3 Is XPath supported? Ans :- Yes, via the XPathXXX classes: XPathDocument xpdoc = new XpathDocument(�test.xml�); XpathNavigator nav = xpdoc.CreateNavigator();


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XpathExpression expr = nav.Compile(�descendant::PEOPLE/PERSON�); XpathNodeIterator iterator = nav.Select(expr); while (iterator.MoveNext()) Console.WriteLine(iterator.Current);

12.5 Threading

12.5.1 Is multi-threading supported? Ans :- Yes, there is extensive support for multi-threading. New threads can be spawned, and there is a system-provided threadpool which applications can use.

12.5.2 How do I spawn a thread? Ans :- Create an instance of a System.Threading.Thread object, passing it an instance of a ThreadStart delegate that will be executed on the new thread. For example: class MyThread { public MyThread( string initData ) { m_data = initData; m_thread = new Thread( new ThreadStart(ThreadMain) ); m_thread.Start(); } // ThreadMain() is executed on the new thread. private void ThreadMain() { Console.WriteLine( m_data ); } public void WaitUntilFinished() { m_thread.Join(); } private Thread m_thread;


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private string m_data; } In this case creating an instance of the MyThread class is sufficient to spawn the thread and execute the MyThread.ThreadMain() method: MyThread t = new MyThread( "Hello, world." ); t.WaitUntilFinished();

12.5.3 How do I stop a thread? Ans :- There are several options. First, you can use your own communication mechanism to tell the ThreadStart method to finish. Alternatively the Thread class has in-built support for instructing the thread to stop. The two principle methods are Thread.Interrupt() and Thread.Abort(). The former will cause a ThreadInterruptedException to be thrown on the thread when it next goes into a WaitJoinSleep state. In other words, Thread.Interrupt is a polite way of asking the thread to stop when it is no longer doing any useful work. In contrast, Thread.Abort() throws a ThreadAbortException regardless of what the thread is doing. Furthermore, the ThreadAbortException cannot normally be caught (though the ThreadStart�s finally method will be executed). Thread.Abort() is a heavy-handed mechanism which should not normally be required.

12.5.4 How do I use the thread pool? Ans :- By passing an instance of a WaitCallback delegate to the ThreadPool.QueueUserWorkItem() method: class Capp { static void Main() { string s = �Hello, World�; ThreadPool.QueueUserWorkItem( new WaitCallback( DoWork ), s ); Thread.Sleep( 1000 ); // Give time for work item to be executed } // DoWork is executed on a thread from the thread pool.


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Static void DoWork( object state ) { Console.WriteLine( state ); } }

12.5.5 How do I know when my thread pool work item has completed? Ans :- There is no way to query the thread pool for this information. You must put code into the WaitCallback method to signal that it has completed. Events are useful for this.

12.5.6 How do I prevent concurrent access to my data? Ans :- Each object has a concurrency lock (critical section) associated with it. The System.Threading.Monitor.Enter/Exit methods are used to acquire and release this lock. For example, instances of the following class only allow one thread at a time to enter method f(): class C { public void f() { try { Monitor.Enter(this); ... } finally { Monitor.Exit(this); } } } C# has a 'lock' keyword which provides a convenient shorthand for the code above: class C { public void f() { lock(this) { ...


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} } } Note that calling Monitor.Enter(myObject) does NOT mean that all access to myObject is serialized. It means that the synchronisation lock associated with myObject has been acquired, and no other thread can acquire that lock until Monitor.Exit(o) is called. In other words, this class is functionally equivalent to the classes above: class C { public void f() { lock( m_object ) { ... } } private m_object = new object(); }

12.6 Tracing

12.6.1 Is there built-in support for tracing/logging? Ans :- Yes, in the System.Diagnostics namespace. There are two main classes that deal with tracing � Debug and Trace. They both work in a similar way � the difference is that tracing from the Debug class only works in builds that have the DEBUG symbol defined, whereas tracing from the Trace class only works in builds that have the TRACE symbol defined. Typically this means that you should use System.Diagnostics.Trace.WriteLine for tracing that you want to work in debug and release builds, and System.Diagnostics.Debug.WriteLine for tracing that you want to work only in debug builds.

12.6.2 Can I redirect tracing to a file? Ans :- Yes. The Debug and Trace classes both have a Listeners property, which is a collection of sinks that receive the tracing that you send via Debug.WriteLine and Trace.WriteLine respectively. By


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default the Listeners collection contains a single sink, which is an instance of the DefaultTraceListener class. This sends output to the Win32 OutputDebugString() function and also the System.Diagnostics.Debugger.Log() method. This is useful when debugging, but if you�re trying to trace a problem at a customer site, redirecting the output to a file is more appropriate. Fortunately, the TextWriterTraceListener class is provided for this purpose. Here�s how to use the TextWriterTraceListener class to redirect Trace output to a file: Trace.Listeners.Clear(); FileStream fs = new FileStream( @�c:\log.txt�, FileMode.Create, FileAccess.Write ); Trace.Listeners.Add( new TextWriterTraceListener( fs ) ); Trace.WriteLine( @�This will be !ustomi to c:\log.txt!� ); Trace.Flush(); Note the use of Trace.Listeners.Clear() to remove the default listener. If you don�t do this, the output will go to the file and OutputDebugString(). Typically this is not what you want, because OutputDebugString() imposes a big performance hit.

12.6.3 Can I !ustomize the trace output? Ans :- Yes. You can write your own TraceListener-derived class, and direct all output through it. Here's a simple example, which derives from TextWriterTraceListener (and therefore has in-built support for writing to files, as shown above) and adds timing information and the thread ID for each trace line: class MyListener : TextWriterTraceListener { public MyListener( Stream s ) : base(s) { } public override void WriteLine( string s ) { Writer.WriteLine( "{0:D8} [{1:D4}] {2}", Environment.TickCount - m_startTickCount, AppDomain.GetCurrentThreadId(), s );


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} protected int m_startTickCount = Environment.TickCount; } (Note that this implementation is not complete - the TraceListener.Write method is not overridden for example.) The beauty of this approach is that when an instance of MyListener is added to the Trace.Listeners collection, all calls to Trace.WriteLine() go through MyListener, including calls made by referenced assemblies that know nothing about the MyListener class.

What platforms support .NET? Right now the only operating system with a full implementation of .NET (that I know about, anyway) is Microsoft Windows. The .NET Framework redistributable is available for Windows 98, Windows NT, Windows 2000, and Windows XP. The .NET Framework SDK is available for Windows 2000 and Windows XP. The Mono Project is an ongoing open-source implementation of .NET for Linux and Windows that is currently still in development. The dotGNU project is another open-source .NET implementation. The Rotor project is a Microsoft shared source CLI implementation targeting Windows and FreeBSD.


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C# FAQ�S

1. Introduction

1.1 What is C#? Ans :- C# is a programming language designed by Microsoft. It is loosely based on C/C++, and bears a striking similarity to Java in many ways. Describe C# as follows: "C# is a simple, modern, object oriented, and type-safe programming language derived from C and C++. C# (pronounced 'C sharp') is firmly planted in the C and C++ family tree of languages, and will immediately be familiar to C and C++ programmers. C# aims to combine the high productivity of Visual Basic and the raw power of C++."

2. Basic types

2.1 What standard types does C# supply? Ans :- C# supports a very similar range of basic types to C++, including int, long, float, double, char, string, arrays, structs and classes. However, don't assume too much. The names may be


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familiar, but some of the details are different. For example, a long is 64 bits in C#, whereas in C++ the size of a long depends on the platform (typically 32 bits on a 32-bit platform, 64 bits on a 64-bit platform). Also classes and structs are almost the same in C++ - this is not true for C#.

2.2 Is it true that all C# types derive from a common base class? Ans :- Yes and no. All types can be treated as if they derive from object (System.Object), but in order to treat an instance of a value type (e.g. int, float) as object-derived, the instance must be converted to a reference type using a process called �boxing�. In theory a developer can forget about this and let the run-time worry about when the conversion is necessary, but in reality this implicit conversion can have side-effects that may trip up the unwary.

2.3 So this means I can pass an instance of a value type to a method that takes an object as a parameter? Ans :- Yes. For example: class Capplication { public static void Main() { int x = 25; string s = �fred�; DisplayMe( x ); DisplayMe( s ); } static void DisplayMe( object o ) { System.Console.WriteLine( �You are {0}�, o ); } } This would display: You are 25 You are fred


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2.4 What are the fundamental differences between value types and reference types? Ans :- C# divides types into two categories - value types and reference types. Most of the basic intrinsic types (e.g. int, char) are value types. Structs are also value types. Reference types include classes, interfaces, arrays and strings. The basic idea is straightforward - an instance of a value type represents the actual data (stored on the stack), whereas an instance of a reference type represents a pointer or reference to the data (stored on the heap). int x1 = 3; // x1 is a value on the stack int x2 = new int(); x2 = 3; // x2 is also a value on the stack!

2.5 Okay, so an int is a value type, and a class is a reference type. How can int be derived from object? It isn't, really. When an int is being used as an int, it is a value (on the stack). However, when it is being used as an object, it is a reference to an integer value on the heap. In other words, when you treat an int as an object, the runtime automatically converts the int value to an object reference. This process is called boxing. The conversion involves copying the contents of the int from the stack to the heap, and creating an object instance which refers to it. Unboxing is the reverse process - the object is converted back to a stack-based value. int x = 3; // new int value 3 on the stack object objx = x; // new int on heap, set to value 3 - still have x=3 on stack int y = (int)objx; // new value 3 on stack, still got x=3 on stack and objx=3 on heap

3. Classes and structs

3.1 Structs are largely redundant in C++. Why does C# have them? Ans :- In C++, a struct and a class are pretty much the same thing. The only difference is the default visibility level (public for structs, private for classes). However, In C# structs and classes are very different. In C#, structs are value types (stored on the stack), whereas classes are reference types (stored on the heap). Also structs cannot inherit from structs or classes, though they can implement interfaces. Structs cannot have destructors.


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3.2 Does C# support multiple inheritance (MI)? Ans :- C# supports multiple inheritance of interfaces, but not of classes.

3.7 What is a static constructor? Ans :- A constructor for a class, rather than instances of a class. The static constructor is called when the class is loaded.

3.8 Are all methods virtual in C#? No. Methods are non-virtual by default, but can be marked as virtual.

3.9 How do I declare a pure virtual function in C#? Ans :- Use the abstract modifier on the method. The class must also be marked as abstract (naturally). Note that abstract methods cannot have an implementation.

4. Exceptions

4.1 Can I use exceptions in C#? Ans :- Yes, in fact exceptions are the recommended error-handling mechanism in C# (and in .NET in general). Most of the .NET framework classes use exceptions to signal errors.

4.2 What types of object can I throw as exceptions? Ans :- Only instances of the System.Exception classes, or classes derived from System.Exception.

4.3 Can I define my own exceptions? Ans :- Yes, as long as you follow the rule that exceptions derive from System.Exception. More specifically, recommend that user-defined exceptions inherit from System.ApplicationException (which is derived from System.Exception).

4.5 Does the System.Exception class have any cool features? Ans :- Yes � the feature which stands out is the StackTrace property. This provides a call stack which records where the exception was thrown from. For example, the following code: using System;


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class Capp { public static void Main() { try { f(); } catch( Exception e ) { Console.WriteLine( �System.Exception stack trace = \n{0}�, e.StackTrace ); } } static void f() { throw new Exception( �f went pear-shaped� ); } } produces this output: System.Exception stack trace = at Capp.f() at Capp.Main() Note, however, that this stack trace was produced from a debug build. A release build may !ptimize away some of the method calls which could mean that the call stack isn�t quite what you expect.

4.6 When should I throw an exception? Ans :- Exceptions should be thrown only when an �unexpected� error occurs. How do you decide if an error is expected or unexpected? This is a judgement call, but a straightforward example of an expected error is failing to read from a file because the seek pointer is at the end of the file, whereas an example of an unexpected error is failing to allocate memory from the heap.

4.7 Does C# have a �throws� clause? Ans :- C# does not require (or even allow) the developer to specify the exceptions that a method can throw.


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5. Run-time type information

5.1 How can I check the type of an object at runtime? You can use the is keyword. For example: using System; class CApp { public static void Main() { string s = "fred"; long i = 10; Console.WriteLine( "{0} is {1}an integer", s, (IsInteger(s) ? "" : "not ") ); Console.WriteLine( "{0} is {1}an integer", i, (IsInteger(i) ? "" : "not ") ); } static bool IsInteger( object obj ) { if( obj is int || obj is long ) return true; else return false; } } produces the output: fred is not an integer 10 is an integer

5.2 Can I get the name of a type at runtime? Ans :- Yes, use the GetType method of the object class (which all types inherit from). For example: using System; class CTest { class CApp


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{ public static void Main() { long i = 10; CTest ctest = new CTest(); DisplayTypeInfo( ctest ); DisplayTypeInfo( i ); } static void DisplayTypeInfo( object obj ) { Console.WriteLine( "Type name = {0}, full type name = {1}", obj.GetType(), obj.GetType().FullName ); } } } produces the following output: Type name = CTest, full type name = CTest Type name = Int64, full type name = System.Int64

6. Advanced language features

6.1 What are delegates? Ans :- A delegate is a class derived from System.Delegate. However the language has a special syntax for declaring delegates which means that they don�t look like classes. A delegate represents a method with a particular signature. An instance of a delegate represents a method with a particular signature on a particular object (or class in the case of a static method). For example: using System; delegate void Stereotype(); class Camerican { public void BePatriotic() { Console.WriteLine( �� <gulp> � God bless America.�); }


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} class Cbrit { public void BeXenophobic() { Console.WriteLine( �Bloody foreigners � � ); } } class Capplication { public static void RevealYourStereotype( Stereotype[] stereotypes ) { foreach( Stereotype s in stereotypes ) s(); } public static void Main() { Camerican chuck = new Camerican(); Cbrit !dward = new Cbrit(); // Create our list of sterotypes. Stereotype[] stereotypes = new Stereotype[2]; stereotypes[0] = new Stereotype( chuck.BePatriotic ); stereotypes[1] = new Stereotype( !dward.BeXenophobic ); // Reveal yourselves! RevealYourStereotype(stereotypes ); } } This produces the following result: � <gulp>� God bless America. Bloody foreigners �


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6.2 Are delegates just like interfaces with a single method? Ans :- Conceptually delegates can be used in a similar way to an interface with a single method. The main practical difference is that with an interface the method name is fixed, whereas with a delegate only the signature is fixed - the method name can be different, as shown in the example above.

7. Miscellaneous

8.1 String comparisons using == seem to be case-sensitive? How do I do a case-insensitive string comparison? Ans :- Use the String.Compare function. Its third parameter is a !oolean which specifies whether case should be ignored or not. �fred� == �Fred� // false System.String.Compare( �fred�, �Fred�, true ) // true

8.2 I�ve seen some string literals which use the @ symbol, and some which don�t. What�s that all about? Ans :- The @ symbol before a string literal means that escape sequences are ignored. This is particularly useful for file names, e.g. string !ilename = �c:\\temp\\test.txt� versus: string !ilename = @�c:\temp\test.txt�

8.3 Does C# support a variable number of arguments? Ans :- Yes, using the params keyword. The arguments are specified as a list of arguments of a specific type, e.g. int. For ultimate flexibility, the type can be object. The standard example of a method which uses this approach is System.Console.WriteLine().

8.4 How can I process command-line arguments? Ans :- Like this:


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using System; class Capp { public static void Main( string[] args ) { Console.WriteLine( �You passed the following arguments:� ); foreach( string arg in args ) Console.WriteLine( arg ); } }

8.5 Does C# do array bounds checking? Ans :- Yes. An IndexOutOfRange exception is used to signal an error.

8.6 How can I make sure my C# classes will interoperate with other .NET languages? Ans :- Make sure your C# code conforms to the Common Language Subset (CLS). To help with this, add the [assembly:CLSCompliant(true)] global attribute to your C# source files. The compiler will emit an error if you use a C# feature which is not CLS-compliant.


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.NET Windows Forms

Q 1. Write a simple Windows Forms Message Box statement. Ans: - System.Windows.Forms.MessageBox.Show ("Hello, Windows Forms");

Q 2. Can you write a class without specifying namespace? Which namespace does it belong to by default??

Ans:- Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you wouldn�t want global namespace.

Q 3. You are designing a GUI application with a window and several widgets on it. The user then resizes the app window and sees a lot of grey space, while the widgets stay in place. What�s the problem?

Ans :- One should use anchoring for correct resizing. Otherwise the default property of a widget on a form is top-left, so it stays at the same location when resized.

Q 4. How can you save the desired properties of Windows Forms application?

Ans :- .config files in .NET are supported through the API to allow storing and retrieving information. They are nothing more than simple XML files, sort of like what .ini files were before for Win32 apps.


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Q 5. So how do you retrieve the customized properties of a .NET application from XML .config file?

Ans: - Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable.

Q 6. Can you automate this process?

Ans :- In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.

Q 7. My progress bar freezes up and dialog window shows blank, when an intensive background process takes over?

Ans :- Yes, you should�ve multi-threaded your GUI, with taskbar and main form being one thread, and the background process being the other

.

Q 8. What�s the safest way to deploy a Windows Forms app?

Ans:- Web deployment: the user always downloads the latest version of the code; the program runs within security sandbox, properly written app will not require additional security privileges.

Q 9. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio?

Ans :- The designer will likely throw it away; most of the code inside InitializeComponent is auto-generated.

Q 10. What�s the difference between WindowsDefaultLocation and WindowsDefaultBounds?

Ans:- WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS.

Q 11. What�s the difference between Move and LocationChanged? Resize and SizeChanged?


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Ans:- Both methods do the same, Move and Resize are the names adopted from VB to ease migration to C#.

Q 12. How would you create a non-rectangular window, let�s say an ellipse?

Ans :- Create a rectangular form, set the TransparencyKey property to the same value as BackColor, which will effectively make the background of the form transparent. Then set the FormBorderStyle to FormBorderStyle.None, which will remove the contour and contents of the form.

Q 13. How do you create a separator in the Menu Designer?

Ans:- A hyphen �-� would do it. Also, an ampersand �&\� would underline the next letter.

Q 14. How�s anchoring different from docking?

Ans:- Anchoring treats the component as having the absolute size and adjusts its location relative to the parent form. Docking treats the component location as absolute and disregards the component size. So if a status bar must always be at the bottom no matter what, use docking. If a button should be on the top right, but change its position with the form being resized, use anchoring.


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.NET Remoting

Q 1. What�s a Windows process?

Ans :- It�s an application that�s running and had been allocated memory.

Q 2. What�s typical about a Windows process in regards to memory allocation?

Ans :- Each process is allocated its own block of available RAM space, no process can access another process� code or data. If the process crashes, it dies alone without taking the entire OS or a bunch of other applications down.

Q 3. Why do you call it a process? What�s different between process and application in .NET, not common computer usage, terminology?

Ans :- A process is an instance of a running application. An application is an executable on the hard drive or network. There can be numerous processes launched of the same application (5 copies of Word running), but 1 process can run just 1 application.

Q 4. What distributed process frameworks outside .NET do you know?

Ans:- Distributed Computing Environment/Remote Procedure Calls (DEC/RPC), Microsoft Distributed Component Object Model (DCOM), Common Object Request Broker Architecture (CORBA), and Java Remote Method Invocation (RMI).

Q 5. What are possible implementations of distributed applications in .NET?


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Ans :- .NET Remoting and ASP.NET Web Services. If we talk about the Framework Class Library, noteworthy classes are in System.Runtime.Remoting and System.Web.Services.

Q 6. When would you use .NET Remoting and when Web services?

Ans:- Use remoting for more efficient exchange of information when you control both ends of the application. Use Web services for open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else.

Q 7. What�s a proxy of the server object in .NET Remoting?

Ans:- It�s a fake copy of the server object that resides on the client side and behaves as if it was the server. It handles the communication between real server object and the client object. This process is also known as marshaling.

Q 8. What are remotable objects in .NET Remoting?

Ans :- Remotable objects are the objects that can be marshaled across the application domains. You can marshal by value, where a deep copy of the object is created and then passed to the receiver. You can also marshal by reference, where just a reference to an existing object is passed.

Q 9. What are channels in .NET Remoting?

Ans:- Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box. A channel must exist before an object can be transferred.

Q 10. What security measures exist for .NET Remoting in System.Runtime.Remoting?

Ans :- None. Security should be taken care of at the application level. Cryptography and other security techniques can be applied at application or server level.

Q 11. What is a formatter?

Ans :- A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.


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Q 12. Choosing between HTTP and TCP for protocols and Binary and SOAP for formatters, what are the trade-offs?

Ans: - Binary over TCP is the most effiecient, SOAP over HTTP is the most interoperable.

Q 13. What�s SingleCall activation mode used for?

Ans :- If the server object is instantiated for responding to just one single request, the request should be made in SingleCall mode.

Q 14. What�s Singleton activation mode?

Ans :- A single object is instantiated regardless of the number of clients accessing it. Lifetime of this object is determined by lifetime lease.

Q 15. How do you define the lease of the object?

Ans:- By implementing ILease interface when writing the class code.

Q 16. Can you configure a .NET Remoting object via XML file?

Ans:- Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config.

Q 17. How can you automatically generate interface for the remotable object in .NET with Microsoft tools?

Ans:- Use the Soapsuds tool.


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Interview Questions ASP.NET

Q 1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process?

Ans :- . inetinfo.exe is theMicrosoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension),the ISAPI filter aspnet_isapi.dll takes care of it by passing the request tothe actual worker process aspnet_wp.exe.

Q 2. What�s the difference between Response.Write() andResponse.Output.Write()?

Ans :- The latter one allows you to write formattedoutput.

Q 3. What methods are fired during the page load?

Ans :- Init() - when the pageis instantiated, Load() - when the page is loaded into server memory,PreRender() - the brief moment before the page is displayed to the user asHTML, Unload() - when page finishes loading.

Q 4. Where does the Web page belong in the .NET Framework class hierarchy?

Ans:- System.Web.UI.Page

Q 5. Where do you store the information about the user�s locale?

Ans :- System.Web.UI.Page.Culture


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Q 6. What�s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?

Ans:- CodeBehind is relevant to Visual Studio.NET only.

Q 7. What�s a bubbled event?

Ans:- When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

Q 8. Suppose you want a certain ASP.NET function executed on MouseOver overa certain button. Where do you add an event handler?

Ans:- It�s the Attributesproperty, the Add function inside that property. So btnSubmit.Attributes.Add("onMouseOver","someClientCode();")

Q 9. What data type does the RangeValidator control support?

Ans:- Integer,String and Date.


Ans:- Server-side code runs on the server. Client-side code runs in the clients� browser.

Q 11. What type of code (server or client) is found in a Code-Behind class?

Ans :- Server-side code.

Q 12. Should validation (did the user enter a real date) occur server-side or client-side? Why?

Ans:- Client-side. This reduces an additional request to the server to validate the users input.

Q 13. What does the "EnableViewState" property do? Why would I want it on or off?

Ans :- It enables the viewstate on the page. It allows the page to save the users input on a form.


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Q 14. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?

Ans :- Server.Transfer is used to post a form to another page. Response.Redirect is used to redirect the user to another page or site.

Q 15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?

Ans :- A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.

• A DataSet is designed to work without any continuing connection to the original data source.

• Data in a DataSet is bulk-loaded, rather than being loaded on demand.

• There's no concept of cursor types in a DataSet.

• DataSets have no current record pointer You can use For Each loops to move through the data.

• You can store many edits in a DataSet, and write them to the original data source in a single operation.

• Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.


Ans :- This is where you can set the specific variables for the Application and Session objects.

Q 17. If I�m developing an application that must accommodate multiple security levels though secure login and my ASP.NET web application is spanned across three web-servers (using round-robin load balancing) what would be the best approach to maintain login-in state for the users?


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Ans:- Maintain the login state security through a database.

Q 18. Can you explain what inheritance is and an example of when you might use it?

Ans :- When you want to inherit (use the functionality of) another class. Base Class Employee. A Manager class could be derived from the Employee base class.

Q 19. Whats an assembly?

Ans :- Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN

Q 20. Describe the difference between inline and code behind?

Ans :- Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page.

Q 21. Explain what a diffgram is, and a good use for one?

Ans:- The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. For reading database data to an XML file to be sent to a Web Service.

Q 22. Whats MSIL, and why should my developers need an appreciation of it if at all?

Ans:- MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL.

Q 23. Which method do you invoke on the DataAdapter control to load your generated dataset with data?

Ans:- The .Fill() method

Q 24. Can you edit data in the Repeater control?

Ans :- No, it just reads the information from its data source

Q 25. Which template must you provide, in order to display data in a Repeater control?


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Ans :- ItemTemplate

Q 26. How can you provide an alternating color scheme in a Repeater control?

Ans:- Use the AlternatingItemTemplate

Q 27. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?

Ans:- You must set the DataSource property and call the DataBind method.

Q 28. What base class do all Web Forms inherit from?

Ans:- The Page class.

Q 29. Name two properties common in every validation control?

And:- ControlToValidate property and Text property.

Q 30. What tags do you need to add within the asp:datagrid tags to bind columns manually?

Ans:- Set AutoGenerateColumns Property to false on the datagrid tag

Q 31. What tag do you use to add a hyperlink column to the DataGrid?

Ans :- <asp:HyperLinkColumn>

Q 32. What is the transport protocol you use to call a Web service?

Ans:- SOAP is the preferred protocol.

Q 33. True or False: A Web service can only be written in .NET?

Ans:- False

Q 34. What does WSDL stand for?

Ans:- (Web Services Description Language)

Q 35. Where on the Internet would you look for Web services?

Ans:- (http://www.uddi.org)


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Q 36. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?

Ans:- DataTextField property

Q 37. Which control would you use if you needed to make sure the values in two different controls matched?

Ans:- CompareValidator Control

Q 38. True or False: To test a Web service you must create a windows application or Web application to consume this service?

Ans:- False, the webservice comes with a test page and it provides HTTP-GET method to test.

Q 39. How many classes can a single .NET DLL contain?

Ans:- It can contain many classes.


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ASP.NET ,C#, VB.NET and COM Full of microsoft Technology

Q 1 .What is view state and use of it?

Ans :- The current property settings of an ASP.NET page and those of any ASP.NET server controls contained within the page. ASP.NET can detect when a form is requested for the first time versus when the form is posted (sent to the server), which allows you to program accordingly. Q 2. What are user controls and custom controls?

Ans :- Custom controls: A control authored by a user or a third-party software vendor that does not belong to the .NET Framework class library. This is a generic term that includes user controls. A custom server control is used in Web Forms (ASP.NET pages). A custom client control is used in Windows Forms applications. User Controls: In ASP.NET: A user-authored server control that enables an ASP.NET page to be re-used as a server control. An ASP.NET user control is authored declaratively and persisted as a text file with an .ascx extension. The ASP.NET page framework compiles a user control on the fly to a class that derives from the System.Web.UI.UserControl class. Q 3. What are the validation controls?


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Ans :- A set of server controls included with ASP.NET that test user input in HTML and Web server controls for programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation using client script.

Q 4. What's the difference between Response.Write() andResponse.Output.Write()?

Ans :- The latter one allows you to write formattedoutput. Q 5. What methods are fired during the page load? Init()

Ans :- When the page is instantiated, Load() - when the page is loaded into server memory,PreRender () - the brief moment before the page is displayed to the user as HTML, Unload() - when page finishes loading. Q.5 Where does the Web page belong in the .NET Framework class hierarchy?

Ans :- System.Web.UI.Page Q 6. Where do you store the information about the user's locale?

Ans :- System.Web.UI.Page.Culture Q 7. What's the difference between Codebehind="MyCode.aspx.cs" and Src="MyCode.aspx.cs"?

Ans :- CodeBehind is relevant to Visual Studio.NET only. Q 8. What's a bubbled event?

Ans :- When you have a complex control, likeDataGrid, writing an event processing routine for each object (cell, button,row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents. Suppose you want a certain ASP.NET function executed on MouseOver over a


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certain button. Q 9.Where do you add an event handler?

Ans :- It's the Attributesproperty, the Add function inside that property. e.g. btnSubmit.Attributes.Add("onMouseOver","someClientCode();") Q 10. What data type does the RangeValidator control support?

Ans :- Integer,String and Date. Q 11. What are the different types of caching?

Ans :- Caching is a technique widely used in computing to increase performance by keeping frequently accessed or expensive data in memory. In context of web application, caching is used to retain the pages or data across HTTP requests and reuse them without the expense of recreating them.ASP.NET has 3 kinds of caching strategiesOutput CachingFragment CachingData

CachingOutput Caching: Caches the dynamic output generated by a request. Some times it is useful to cache the output of a website even for a minute, which will result in a better performance. For caching the whole page the page should have OutputCache directive.<%@ OutputCache Duration="60" VaryByParam="state" %>

Fragment Caching: Caches the portion of the page generated by the request. Some times it is not practical to cache the entire page, in such cases we can cache a portion of page<%@ OutputCache Duration="120" VaryByParam="CategoryID;SelectedID"%>

Data Caching: Caches the objects programmatically. For data caching asp.net provides a cache object for eg: cache["States"] = dsStates; Q 12. What do you mean by authentication and authorization?

Ans :- Authentication is the process of validating a user on the credentials (username and password) and authorization performs after authentication. After Authentication a user will be verified for performing the various tasks, It access is limited it is known as authorization. Q 13. What are different types of directives in .NET?


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Ans :- @Page: Defines page-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .aspx files <%@ Page AspCompat="TRUE" language="C#" %> @Control:Defines control-specific attributes used by the ASP.NET page parser and compiler. Can be included only in .ascx files. <%@ Control Language="VB" EnableViewState="false" %> @Import: Explicitly imports a namespace into a page or user control. The Import directive cannot have more than one namespace attribute. To import multiple namespaces, use multiple @Import directives. <% @ Import Namespace="System.web" %> @Implements: Indicates that the current page or user control implements the specified .NET framework interface.<%@ Implements Interface="System.Web.UI.IPostBackEventHandler" %> @Register: Associates aliases with namespaces and class names for concise notation in custom server control syntax.<%@ Register Tagprefix="Acme" Tagname="AdRotator" Src="AdRotator.ascx" %> @Assembly: Links an assembly to the current page during compilation, making all the assembly's classes and interfaces available for use on the page. <%@ Assembly Name="MyAssembly" %><%@ Assembly Src="MySource.vb" %> @OutputCache: Declaratively controls the output caching policies of an ASP.NET page or a user control contained in a page<%@ OutputCache Duration="#ofseconds" Location="Any | Client | Downstream | Server | None" Shared="True | False" VaryByControl="controlname" VaryByCustom="browser | customstring" VaryByHeader="headers" VaryByParam="parametername" %> @Reference: Declaratively indicates that another user control or page source file should be dynamically compiled and linked against the page in which this directive is declared.

Q 14. How do I debug an ASP.NET application that wasn't written with Visual Studio.NET and that doesn't use code-behind?

Ans :- Start the DbgClr debugger that comes with the .NET Framework SDK, open the file containing the code you want to debug, and set your breakpoints. Start the ASP.NET application. Go back to DbgClr, choose Debug Processes from the Tools menu, and select aspnet_wp.exe from the list of processes. (If aspnet_wp.exe doesn't appear in the list,check the "Show system processes" box.) Click the Attach button to attach to aspnet_wp.exe and begin debugging. Be sure to enable debugging in the ASPX file before debugging it with DbgClr. You can enable tell ASP.NET to build debug executables by placing a


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<%@ Page Debug="true" %> statement at the top of an ASPX file or a <COMPILATION debug="true" />statement in a Web.config file. Q 15. Can a user browsing my Web site read my Web.config or Global.asax files?

Ans :- No. The <HTTPHANDLERS>section of Machine.config, which holds the master configuration settings for ASP.NET, contains entries that map ASAX files, CONFIG files, and selected other file types to an HTTP handler named HttpForbiddenHandler, which fails attempts to retrieve the associated file. You can modify it by editing Machine.config or including an section in a local Web.config file. Q 16. What's the difference between Page.RegisterClientScriptBlock and Page.RegisterStartupScript?

Ans :- RegisterClientScriptBlock is for returning blocks of client-side script containing functions. RegisterStartupScript is for returning blocks of client-script not packaged in functions-in other words, code that's to execute when the page is loaded. The latter positions script blocks near the end of the document so elements on the page that the script interacts are loaded before the script runs.<%@ Reference Control="MyControl.ascx" %>

Q 17. Is it necessary to lock application state before accessing it?

Ans:- Only if you're performing a multistep update and want the update to be treated as an atomic operation. Here's an example: Application.Lock (); Application["ItemsSold"] = (int) Application["ItemsSold"] + 1; Application["ItemsLeft"] = (int) Application["ItemsLeft"] - 1; Application.UnLock (); By locking application state before updating it and unlocking it afterwards, you ensure that another request being processed on another thread doesn't read application state at exactly the wrong time and see an inconsistent view of it. If I update session state, should I lock it, too? Are concurrent accesses by multiple requests executing on multiple threads a concern with session state? Concurrent accesses aren't an issue with session state, for two reasons. One, it's unlikely that two requests from the same user will overlap. Two, if they do overlap, ASP.NET locks down session state during request processing so that two threads can't touch it at once. Session state is locked down when the HttpApplication


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instance that's processing the request fires an AcquireRequestState event and unlocked when it fires a ReleaseRequestState event.

Do ASP.NET forms authentication cookies provide any protection against replay attacks? Do they, for example, include the client's IP address or anything else that would distinguish the real client from an attacker? No. If an authentication cookie is stolen, it can be used by an attacker. It's up to you to prevent this from happening by using an encrypted communications channel (HTTPS). Authentication cookies issued as session cookies, do, however,include a time-out valid that limits their lifetime. So a stolen session cookie can only be used in replay attacks as long as the ticket inside the cookie is valid. The default time-out interval is 30 minutes.You can change that by modifying the timeout attribute accompanying the <forms> element in Machine.config or a local Web.config file. Persistent authentication cookies do not time-out and therefore are a more serious security threat if stolen.

Q 18. How do I send e-mail from an ASP.NET application?

Ans :- MailMessage message = new MailMessage (); message.From = <email>; message.To = <email>; message.Subject = "Scheduled Power Outage"; message.Body = "Our servers will be down tonight."; SmtpMail.SmtpServer = "localhost"; SmtpMail.Send (message);

MailMessage and SmtpMail are classes defined in the .NET Framework Class Library's System.Web.Mail namespace. Due to a security change made to ASP.NET just before it shipped, you need to set SmtpMail's SmtpServer property to "localhost" even though "localhost" is the default. In addition, you must use the IIS configuration applet to enable localhost (127.0.0.1) to relay messages through the local SMTP service.

Q 19. What are VSDISCO files?

Ans :- VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns references to all ASMX and DISCO files in the host directory and any subdirectories not noted in <exclude> elements:


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<?xml version="1.0" ?> <dynamicDiscovery xmlns="urn:schemas-dynamicdiscovery:disco.2000-03-17"> <exclude path="_vti_cnf" /> <exclude path="_vti_pvt" /> <exclude path="_vti_log" /> <exclude path="_vti_script" /> <exclude path="_vti_txt" /> </dynamicDiscovery>

Q 20. How does dynamic discovery work?

Ans :- ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document. Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line in the <httpHandlers> section of Machine.config that maps *.vsdisco to System.Web.Services.Discovery.DiscoveryRequestHandler and granting the ASPNET user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security. Q 21. Is it possible to prevent a browser from caching an ASPX page?

Ans :- Just call SetNoStore on the HttpCachePolicy object exposed through the Response object's Cache property, as demonstrated here: <%@ Page Language="C#" %> <html> <body> <% Response.Cache.SetNoStore (); Response.Write (DateTime.Now.ToLongTimeString ()); %> </body> </html>


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SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time.

Q 22. What does AspCompat="true" mean and when should I use it?

Ans :- AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects--that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true:

<%@ Page AspCompat="true" %>

Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat="true" forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat="true," request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it's marshaled across apartment boundaries.

Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don't access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both.


Ans :- Server side scripting means that all the script will be executed by the server and interpreted as needed. ASP doesn't have some of the functionality like sockets, uploading, etc. For these you have to make a custom components usually in VB or VC++. Client side scripting means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript. Download time, browser


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compatibility, and visible code - since JavaScript and VBScript code is included in the HTML page, then anyone can see the code by viewing the page source. Also a possible security hazards for the client computer.


Ans :- C#


Ans :- Client-side validation because there is no need to request a server side date when you could obtain a date from the client machine.

Q 26. What are ASP.NET Web Forms? How is this technology different than what is available though ASP?

Ans :- Web Forms are the heart and soul of ASP.NET. Web Forms are the User Interface (UI) elements that give your Web applications their look and feel. Web Forms are similar to Windows Forms in that they provide properties, methods, and events for the controls that are placed onto them. However, these UI elements render themselves in the appropriate markup language required by the request, e.g. HTML. If you use Microsoft Visual Studio .NET, you will also get the familiar drag-and-drop interface used to create your UI for your Web application.


Ans :- In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they're difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.


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Q 28. How can you provide an alternating color scheme in a Repeater control?

Ans :- AlternatingItemTemplate Like the ItemTemplate element, but rendered for every other row (alternating items) in the Repeater control. You can specify a different appearance for the AlternatingItemTemplate element by setting its style properties.

Q 29 Which template must you provide, in order to display data in a Repeater control?

Ans: -ItemTemplate

Q 30. What event handlers can I include in Global.asax?

Ans :- Application_Start,Application_End, Application_AcquireRequestState, Application_AuthenticateRequest, Application_AuthorizeRequest, Application_BeginRequest, Application_Disposed, Application_EndRequest, Application_Error, Application_PostRequestHandlerExecute, Application_PreRequestHandlerExecute, Application_PreSendRequestContent, Application_PreSendRequestHeaders, Application_ReleaseRequestState, Application_ResolveRequestCache, Application_UpdateRequestCache, Session_Start,Session_End You can optionally include "On" in any of method names. For example, you can name a BeginRequest event handler.Application_BeginRequest or Application_OnBeginRequest.You can also include event handlers in Global.asax for events fired by custom HTTP modules.Note that not all of the event handlers make sense for Web Services (they're designed for ASP.NET applications in general, whereas .NET XML Web Services are specialized instances of an ASP.NET app). For example, the Application_AuthenticateRequest and Application_AuthorizeRequest events are designed to be used with ASP.NET Forms authentication.

Q 31. What is different b/w webconfig.xml & Machineconfig.xml

Ans :- Web.config & machine.config both are configuration files.Web.config contains settings specific to an application where as machine.config contains settings to a computer. The Configuration system first searches settings in machine.config file & then looks in application configuration files.Web.config, can appear in multiple directories on an ASP.NET Web application server. Each Web.config file applies


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configuration settings to its own directory and all child directories below it. There is only Machine.config file on a web server.

If I'm developing an application that must accomodate multiple security levels though secure login and my ASP.NET web appplication is spanned across three web-servers (using round-robbin load balancing) what would be the best approach to maintain login-in state for the users? Use the state server or store the state in the database. This can be easily done through simple setting change in the web.config. <SESSIONSTATE StateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1; user id=sa; password=" cookieless="false" timeout="30" />

You can specify mode as �stateserver� or �sqlserver�.

Where would you use an iHTTPModule, and what are the limitations of any approach you might take in implementing one "One of ASP.NET's most useful features is the extensibility of the HTTP pipeline, the path that data takes between client and server. You can use them to extend your ASP.NET applications by adding pre- and post-processing to each HTTP request coming into your application. For example, if you wanted custom authentication facilities for your application, the best technique would be to intercept the request when it comes in and process the request in a custom HTTP module.

Q 32.How do you turn off cookies for one page in your site?

Ans :- Since no Page Level directive is present, I am afraid that cant be done.

Q 33. How do you create a permanent cookie?

Ans:- Permanent cookies are available until a specified expiration date, and are stored on the hard disk.So Set the 'Expires' property any value greater than DataTime.MinValue with respect to the current datetime. If u want the cookie which never expires set its Expires property equal to DateTime.maxValue.

Q 34 Which method do you use to redirect the user to another page without performing a round trip to the client?


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Ans :- Server.Transfer and Server.Execute

Q 35 . What property do you have to set to tell the grid which page to go to when using the Pager object?

Ans :- CurrentPageIndex


Ans :- It should occur both at client-side and Server side.By using expression validator control with the specified expression ie.. the regular expression provides the facility of only validatating the date specified is in the correct format or not. But for checking the date where it is the real data or not should be done at the server side, by getting the system date ranges and checking the date whether it is in between that range or not.

Q 37. What does the "EnableViewState" property do? Why would I want it on or off?

Ans :- Enable ViewState turns on the automatic state management feature that enables server controls to re-populate their values on a round trip without requiring you to write any code. This feature is not free however, since the state of a control is passed to and from the server in a hidden form field. You should be aware of when ViewState is helping you and when it is not. For example, if you are binding a control to data on every round trip, then you do not need the control to maintain it's view state, since you will wipe out any re-populated data in any case. ViewState is enabled for all server controls by default. To disable it, set the EnableViewState property of the control to false.


Ans :- Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist accros the pages using


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Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.

Response.Dedirect() :client know the physical location (page name and query string as well). Context.Items loses the persisitance when nevigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they're difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client.

Q 39. Can you give an example of when it would be appropriate to use a web service as opposed to a non-serviced .NET component?

Ans :- Communicating through a Firewall When building a distributed application with 100s/1000s of users spread over multiple locations, there is always the problem of communicating between client and server because of firewalls and proxy servers. Exposing your middle tier components as Web Services and invoking the directly from a Windows UI is a very valid option.

• Application Integration When integrating applications written in various languages and running on disparate systems. Or even applications running on the same platform that have been written by separate vendors.

• Business-to-Business Integration This is an enabler for B2B intergtation which allows one to expose vital business processes to authorized supplier and customers. An example would be exposing electronic ordering and invoicing, allowing customers to send you purchase orders and suppliers to send you invoices electronically.

• Software Reuse This takes place at multiple levels. Code Reuse at the Source code level or binary componet-based resuse. The limiting factor here is that you can reuse the code but not the data behind it. Webservice overcome this limitation. A scenario could be when you are building an app that aggregates


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the functionality of serveral other Applicatons. Each of these functions could be performed by individual apps, but there is value in perhaps combining the the multiple apps to present a unifiend view in a Portal or Intranet.

• When not to use Web Services: Single machine Applicatons When the apps are running on the same machine and need to communicate with each other use a native API. You also have the options of using component technologies such as COM or .NET Componets as there is very little overhead.

• Homogeneous Applications on a LAN If you have Win32 or Winforms apps that want to communicate to their server counterpart. It is much more efficient to use DCOM in the case of Win32 apps and .NET Remoting in the case of .NET Apps


Ans :- The Application_Start event is guaranteed to occur only once throughout the lifetime of the application. It's a good place to initialize global variables. For example, you might want to retrieve a list of products from a database table and place the list in application state or the Cache object. SessionStateModule exposes both Session_Start and Session_End events.

Q 41. What are the advantages and disadvantages of viewstate?

Ans:- The primary advantages of the ViewState feature in ASP.NET are:

1. Simplicity. There is no need to write possibly complex code to store form data between page submissions. 2. Flexibility. It is possible to enable, configure, and disable ViewState on a control-by-control basis, choosing to persist the values of some fields but not others.

There are, however a few disadvantages that are worth pointing out:

1. Does not track across pages. ViewState information does not automatically transfer from page to page. With the session approach, values can be stored in the session and accessed from other pages. This is not possible with ViewState, so storing data into the session must be done explicitly.


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2. ViewState is not suitable for transferring data for back-end systems. That is, data still has to be transferred to the back end using some form of data object.

Q 42. Describe session handling in a webfarm, how does it work and what are the limits? ASP.NET Session supports storing of session data in 3 ways, i] in In-Process ( in the same memory that ASP.NET uses) , ii] out-of-process using Windows NT Service )in separate memory from ASP.NET ) or iii] in SQL Server (persistent storage). Both the Windows Service and SQL Server solution support a webfarm scenario where all the web-servers can be configured to share common session state store. 1. Windows Service : We can start this service by Start | Control Panel | Administrative Tools | Services | . In that we service names ASP.NET State Service. We can start or stop service by manually or configure to start automatically. Then we have to configure our web.config file

<CONFIGURATION><configuration> <system.web> <SessionState mode = �StateServer� stateConnectionString = �tcpip=127.0.0.1:42424� stateNetworkTimeout = �10� sqlConnectionString=�data source = 127.0.0.1; uid=sa;pwd=� cookieless =�Flase� timeout= �20� /> </system.web> </configuration> </SYSTEM.WEB> </CONFIGURATION> Here ASP.Net Session is directed to use Windows Service for state management on local server (address : 127.0.0.1 is TCP/IP loop-back address). The default port is 42424. we can configure to any port but for that we have to manually edit the registry. Follow these simple steps - In a webfarm make sure you have the same config file in all your web servers.


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- Also make sure your objects are serializable. - For session state to be maintained across different web servers in the webfarm, the application path of the web-site in the IIS Metabase should be identical in all the web-servers in the webfarm.

Q 43. Which template must you provide, in order to display data in a Repeater control?

Ans : -You have to use the ItemTemplate to Display data. Syntax is as follows, < ItemTemplate > < div class =�rItem� > < img src=�images/<%# Container.DataItem(�ImageURL�)%>� hspace=�10� /> < b > <% # Container.DataItem(�Title�)%> < /div > < ItemTemplate >

Q 44.How can you provide an alternating color scheme in a Repeater control?

Ans :- Using the AlternatintItemTemplate

Q 45. What property must you set, and what method must you call in your code, in order to bind the data from some data source to the Repeater control?

Ans :- Set the DataMember property to the name of the table to bind to. (If this property is not set, by default the first table in the dataset is used.) DataBind method, use this method to bind data from a source to a server control. This method is commonly used after retrieving a data set through a database query.

Q 46. What method do you use to explicitly kill a user s session?

Ans :- You can dump (Kill) the session yourself by calling the method Session.Abandon.

ASP.NET automatically deletes a user's Session object, dumping its contents, after it has been idle for a configurable timeout interval. This interval, in minutes, is set in the <SESSIONSTATE>section of the web.config file. The default is 20 minutes.


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Q 47. How do you turn off cookies for one page in your site?

Ans :- Use Cookie.Discard property, Gets or sets the discard flag set by the server. When true, this property instructs the client application not to save the Cookie on the user's hard disk when a session ends.

Q 48. Which two properties are on every validation control?

Ans :- We have two common properties for every validation controls 1. Control to Validate, 2. Error Message.


Ans:- < asp:DataGrid id="dgCart" AutoGenerateColumns="False" CellPadding="4" Width="448px" runat="server" > < Columns > < asp:ButtonColumn HeaderText="SELECT" Text="SELECT" CommandName="select" >< /asp:ButtonColumn > < asp:BoundColumn DataField="ProductId" HeaderText="Product ID" >< /asp:BoundColumn > < asp:BoundColumn DataField="ProductName" HeaderText="Product Name" >< /asp:BoundColumn > < asp:BoundColumn DataField="UnitPrice" HeaderText="UnitPrice" >< /asp:BoundColumn > < /Columns > < /asp:DataGrid >

Q 50. How do you create a permanent cookie?

Ans :- Permanent cookies are the ones that are most useful. Permanent cookies are available until a specified expiration date, and are stored on the hard disk. The location of cookies differs with each browser, but this doesn�t matter, as this is all handled by your browser and the server. If you want to create a permanent cookie called Name with a value of Nigel, which expires in one month, you�d use the following code


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Response.Cookies ("Name") = "Nigel" Response.Cookies ("Name"). Expires = DateAdd ("m", 1, Now ())

Q 51. What tag do you use to add a hyperlink column to the DataGrid?

Ans :- < asp:HyperLinkColumn > </ asp:HyperLinkColumn>

Q 52. Which method do you use to redirect the user to another page without performing a round trip to the client?

Ans :- Server.transfer

Q 52. What is the transport protocol you use to call a Web service SOAP ?

Ans :- HTTP Protocol

Q 53. Explain role based security ?

Ans :- Role Based Security lets you identify groups of users to allow or deny based on their role in the organization.In Windows NT and Windows XP, roles map to names used to identify user groups. Windows defines several built-in groups, including Administrators, Users, and Guests.To allow or deny access to certain groups of users, add the <ROLES>element to the authorization list in your Web application's Web.config file.e.g. <AUTHORIZATION>< authorization > < allow roles="Domain Name\Administrators" / > < !-- Allow Administrators in domain. -- > < deny users="*" / > < !-- Deny anyone else. -- > < /authorization >

Q 54. How do you register JavaScript for webcontrols ?

Ans :- You can register javascript for controls using <CONTROL -name>Attribtues.Add(scriptname,scripttext) method.


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Q 55. When do you set "<IDENTITY impersonate="true" />" ?

Ans :- Identity is a webconfig declaration under System.web, which helps to control the application Identity of the web applicaton. Which can be at any level(Machine,Site,application,subdirectory,or page), attribute impersonate with "true" as value specifies that client impersonation is used.

Q 56. What are different templates available in Repeater,DataList and Datagrid ?

Ans ;- Templates enable one to apply complicated formatting to each of the items displayed by a control.Repeater control supports five types of templates.HeaderTemplate controls how the header of the repeater control is formatted.ItemTemplate controls the formatting of each item displayed.AlternatingItemTemplate controls how alternate items are formatted and the SeparatorTemplate displays a separator between each item displyed.FooterTemplate is used for controlling how the footer of the repeater control is formatted.The DataList and Datagrid supports two templates in addition to the above five.SelectedItem Template controls how a selected item is formatted and EditItemTemplate controls how an item selected for editing is formatted.

Q 57. What is ViewState ? and how it is managed ?

Ans ;- ASP.NET ViewState is a new kind of state service that developers can use to track UI state on a per-user basis. Internally it uses an an old Web programming trick-roundtripping state in a hidden form field and bakes it right into the page-processing framework.It needs less code to write and maintain state in your Web-based forms.

Q 58. What is web.config file ?

Ans :- Web.config file is the configuration file for the Asp.net web application. There is one web.config file for one asp.net application which configures the particular application. Web.config file is written in XML with specific tags having specific meanings.It includes databa which includes connections,Session States,Error Handling,Security etc. For example :

< configuration > < appSettings >


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< add key="ConnectionString" value="server=localhost;uid=sa;pwd=;database=MyDB" / > < /appSettings > < /configuration >

Q 59. What is advantage of viewstate and what are benefits?

Ans :- When a form is submitted in classic ASP, all form values are cleared. Suppose you have submitted a form with a lot of information and the server comes back with an error. You will have to go back to the form and correct the information. You click the back button, and what happens.......ALL form values are CLEARED, and you will have to start all over again! The site did not maintain your ViewState.With ASP .NET, the form reappears in the browser window together with all form values.This is because ASP .NET maintains your ViewState. The ViewState indicates the status of the page when submitted to the server.


Ans :- Set AutoGenerateColumns Property to false on the datagrid tag and then use Column tag and an ASP:databound tag

< asp:DataGrid runat="server" id="ManualColumnBinding" AutoGenerateColumns="False" > < Columns > < asp:BoundColumn HeaderText="Column1" DataField="Column1"/ > < asp:BoundColumn HeaderText="Column2" DataField="Column2"/ > < /Columns > < /asp:DataGrid > <asp:DataGrid id=ManualColumnBinding runat="server" AutoGenerateColumns="False"> <COLUMNS> <asp:BoundColumn HeaderText="Column2" DataField="Column2"></asp:BoundColumn> </asp:DataGrid>

Q 61. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?


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Ans :- DataTextField and DataValueField

Q 62. Which control would you use if you needed to make sure the values in two different controls matched?

Ans :- CompareValidator is used to ensure that two fields are identical.

Q 63. What is validationsummary server control?where it is used?.

Ans :- The ValidationSummary control allows you to summarize the error messages from all validation controls on a Web page in a single location. The summary can be displayed as a list, a bulleted list, or a single paragraph, based on the value of the DisplayMode property. The error message displayed in the ValidationSummary control for each validation control on the page is specified by the ErrorMessage property of each validation control. If the ErrorMessage property of the validation control is not set, no error message is displayed in the ValidationSummary control for that validation control. You can also specify a custom title in the heading section of the ValidationSummary control by setting the HeaderText property. You can control whether the ValidationSummary control is displayed or hidden by setting the ShowSummary property. The summary can also be displayed in a message box by setting the ShowMessageBox property to true.

Q 64. What is the sequence of operation takes place when a page is loaded?

Ans :- BeginTranaction - only if the request is transacted Init - every time a page is processed LoadViewState - Only on postback ProcessPostData1 - Only on postback Load - every time ProcessData2 - Only on Postback RaiseChangedEvent - Only on Postback RaisePostBackEvent - Only on Postback PreRender - everytime BuildTraceTree - only if tracing is enabled SaveViewState - every time Render - Everytime End Transaction - only if the request is transacted Trace.EndRequest - only when tracing is enabled UnloadRecursive - Every request


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Q 65. Difference between asp and asp.net?.

Ans :- "ASP (Active Server Pages) and ASP.NET are both server side technologies for building web sites and web applications, ASP.NET is Managed compiled code - asp is interpreted. and ASP.net is fully Object oriented. ASP.NET has been entirely re-architected to provide a highly productive programming experience based on the .NET Framework, and a robust infrastructure for building reliable and scalable web applications."

Q 66. Name the validation control available in asp.net?.

Ans :-RequiredField, RangeValidator,RegularExpression,Custom validator,compare Validator

Q67. What are the various ways of securing a web site that could prevent from hacking etc .. ?

Ans :- 1) Authentication/Authorization 2) Encryption/Decryption 3) Maintaining web servers outside the corporate firewall. etc.,

Q 68. What is the difference between in-proc and out-of-proc?

Ans :- An inproc is one which runs in the same process area as that of the client giving tha advantage of speed but the disadvantage of stability becoz if it crashes it takes the client application also with it.Outproc is one which works outside the clients memory thus giving stability to the client, but we have to compromise a bit on speed.

Q 69. When you�re running a component within ASP.NET, what process is it running within on Windows XP? Windows 2000? Windows 2003?

Ans :- On Windows 2003 (IIS 6.0) running in native mode, the component is running within the w3wp.exe process associated with the application pool which has been configured for the web application containing the component.


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On Windows 2003 in IIS 5.0 emulation mode, 2000, or XP, it's running within the IIS helper process whose name I do not remember, it being quite a while since I last used IIS 5.0.

Q 70. What does aspnet_regiis -i do ?

Ans :- Aspnet_regiis.exe is The ASP.NET IIS Registration tool allows an administrator or installation program to easily update the script maps for an ASP.NET application to point to the ASP.NET ISAPI version associated with the tool. The tool can also be used to display the status of all installed versions of ASP. NET, register the ASP.NET version coupled with the tool, create client-script directories, and perform other configuration operations. When multiple versions of the .NET Framework are executing side-by-side on a single computer, the ASP.NET ISAPI version mapped to an ASP.NET application determines which version of the common language runtime is used for the application. The tool can be launched with a set of optional parameters. Option "i" Installs the version of ASP.NET associated with Aspnet_regiis.exe and updates the script maps at the IIS metabase root and below. Note that only applications that are currently mapped to an earlier version of ASP.NET are affected

Q 71. What is a PostBack?

Ans : - The process in which a Web page sends data back to the same page on the server.

Q 72. What is ViewState? How is it encoded? Is it encrypted? Who uses ViewState?

Ans:- ViewState is the mechanism ASP.NET uses to keep track of server control state values that don't otherwise post back as part of the HTTP form. ViewState Maintains the UI State of a Page ViewState is base64-encoded. It is not encrypted but it can be encrypted by setting EnableViewStatMAC="true" & setting the machineKey validation type to 3DES. If you want to NOT maintain the ViewState, include the directive < %@ Page EnableViewState="false" % > at the top of an .aspx page or add the attribute EnableViewState="false" to any control.


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Q 73. What is the < machinekey > element and what two ASP.NET technologies is it used for?

Ans :- Configures keys to use for encryption and decryption of forms authentication cookie data and view state data, and for verification of out-of-process session state identification.There fore 2 ASP.Net technique in which it is used are Encryption/Decryption & Verification

Q 74. What three Session State providers are available in ASP.NET 1.1? What are the pros and cons of each?

Ans :- ASP.NET provides three distinct ways to store session data for your application: in-process session state, out-of-process session state as a Windows service, and out-of-process session state in a SQL Server database. Each has it advantages.

1.In-process session-state mode Limitations: * When using the in-process session-state mode, session-state data is lost if aspnet_wp.exe or the application domain restarts. * If you enable Web garden mode in the < processModel > element of the application's Web.config file, do not use in-process session-state mode. Otherwise, random data loss can occur. Advantage: * in-process session state is by far the fastest solution. If you are storing only small amounts of volatile data in session state, it is recommended that you use the in-process provider.

2. The State Server simply stores session state in memory when in out-of-proc mode. In this mode the worker process talks directly to the State Server

3. SQL mode, session states are stored in a SQL Server database and the worker process talks directly to SQL. The ASP.NET worker processes are then able to take advantage of this simple storage service by serializing and saving (using .NET serialization services) all objects within a client's Session collection at the end of each Web request Both these out-of-process solutions are useful primarily if you scale your application across multiple processors or multiple computers, or where data cannot be lost if a server or process is restarted.


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Q 75. What is the difference between HTTP-Post and HTTP-Get?

Ans :- As their names imply, both HTTP GET and HTTP POST use HTTP as their underlying protocol. Both of these methods encode request parameters as name/value pairs in the HTTP request. The GET method creates a query string and appends it to the script's URL on the server that handles the request. The POST method creates a name/value pairs that are passed in the body of the HTTP request message.

Q 76. Name and describe some HTTP Status Codes and what they express to the requesting client.

Ans :- When users try to access content on a server that is running Internet Information Services (IIS) through HTTP or File Transfer Protocol (FTP), IIS returns a numeric code that indicates the status of the request. This status code is recorded in the IIS log, and it may also be displayed in the Web browser or FTP client. The status code can indicate whether a particular request is successful or unsuccessful and can also reveal the exact reason why a request is unsuccessful. There are 5 groups ranging from 1xx - 5xx of http status codes exists. 101 - Switching protocols. 200 - OK. The client request has succeeded 302 - Object moved. 400 - Bad request. 500.13 - Web server is too busy.

Q 77. Explain < @OutputCache% > and the usage of VaryByParam, VaryByHeader?

Ans :- OutputCache is used to control the caching policies of an ASP.NET page or user control. To cache a page @OutputCache directive should be defined as follows < %@ OutputCache Duration="100" VaryByParam="none" % >

VaryByParam: A semicolon-separated list of strings used to vary the output cache. By default, these strings correspond to a query string value sent with GET method attributes, or a parameter sent using the POST method. When this attribute is set to multiple parameters, the output cache contains a different version of the requested document for each specified parameter. Possible values include none, *, and any valid query string or POST parameter name.


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VaryByHeader: A semicolon-separated list of HTTP headers used to vary the output cache. When this attribute is set to multiple headers, the output cache contains a different version of the requested document for each specified header.

Q 78. What is the difference between repeater over datalist and datagrid?

Ans :- The Repeater class is not derived from the WebControl class, like the DataGrid and DataList. Therefore, the Repeater lacks the stylistic properties common to both the DataGrid and DataList. What this boils down to is that if you want to format the data displayed in the Repeater, you must do so in the HTML markup. The Repeater control provides the maximum amount of flexibility over the HTML produced. Whereas the DataGrid wraps the DataSource contents in an HTML < table >, and the DataList wraps the contents in either an HTML < table > or < span > tags (depending on the DataList's RepeatLayout property), the Repeater adds absolutely no HTML content other than what you explicitly specify in the templates. While using Repeater control, If we wanted to display the employee names in a bold font we'd have to alter the "ItemTemplate" to include an HTML bold tag, Whereas with the DataGrid or DataList, we could have made the text appear in a bold font by setting the control's ItemStyle-Font-Bold property to True. The Repeater's lack of stylistic properties can drastically add to the development time metric. For example, imagine that you decide to use the Repeater to display data that needs to be bold, centered, and displayed in a particular font-face with a particular background color. While all this can be specified using a few HTML tags, these tags will quickly clutter the Repeater's templates. Such clutter makes it much harder to change the look at a later date. Along with its increased development time, the Repeater also lacks any built-in functionality to assist in supporting paging, editing, or editing of data. Due to this lack of feature-support, the Repeater scores poorly on the usability scale.

However, The Repeater's performance is slightly better than that of the DataList's, and is more noticeably better than that of the DataGrid's. Following figure shows the number of requests per second the Repeater could handle versus the DataGrid and DataList

Q 79. Can we handle the error and redirect to some pages using web.config?

Yes, we can do this, but to handle errors, we must know the error codes; only then we can take the user to a proper error message page, else it may confuse the user. CustomErrors Configuration section in web.config file: The default configuration is:


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< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" > < error statusCode="404" redirect="Notfound.aspx" / > < /customErrors > If mode is set to Off, custom error messages will be disabled. Users will receive detailed exception error messages. If mode is set to On, custom error messages will be enabled. If mode is set to RemoteOnly, then users will receive custom errors, but users accessing the site locally will receive detailed error messages. Add an < error > tag for each error you want to handle. The error tag will redirect the user to the Notfound.aspx page when the site returns the 404 (Page not found) error.

[Example]

There is a page MainForm.aspx

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 'Put user code to initialize the page here Dim str As System.Text.StringBuilder str.Append("hi") ' Error Line as str is not instantiated Response.Write(str.ToString) End Sub

[Web.Config]

< customErrors mode="On" defaultRedirect="Error.aspx"/ > ' a simple redirect will take the user to Error.aspx [user defined] error file.

< customErrors mode="RemoteOnly" defaultRedirect="Customerror.aspx" > < error statusCode="404" redirect="Notfound.aspx" / > < /customErrors > 'This will take the user to NotFound.aspx defined in IIS.

Q 80. How do you implement Paging in .Net?

Ans :- The DataGrid provides the means to display a group of records from the data source (for example, the first 10), and then navigate to the "page" containing the next 10 records, and so on through the data.


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Using Ado.Net we can explicit control over the number of records returned from the data source, as well as how much data is to be cached locally in the DataSet. 1.Using DataAdapter.fill method give the value of 'Maxrecords' parameter (Note: - Don't use it because query will return all records but fill the dataset based on value of 'maxrecords' parameter). 2.For SQL server database, combines a WHERE clause and a ORDER BY clause with TOP predicate. 3.If Data does not change often just cache records locally in DataSet and just take some records from the DataSet to display.

Q 81. What is the difference between Server.Transfer and Response.Redirect?

Ans :- Server.Transfer() : client is shown as it is on the requesting page only, but the all the content is of the requested page. Data can be persist across the pages using Context.Item collection, which is one of the best way to transfer data from one page to another keeping the page state alive.

Response.Dedirect() :client knows the physical location (page name and query string as well). Context.Items loses the persistence when navigate to destination page. In earlier versions of IIS, if we wanted to send a user to a new Web page, the only option we had was Response.Redirect. While this method does accomplish our goal, it has several important drawbacks. The biggest problem is that this method causes each page to be treated as a separate transaction. Besides making it difficult to maintain your transactional integrity, Response.Redirect introduces some additional headaches. First, it prevents good encapsulation of code. Second, you lose access to all of the properties in the Request object. Sure, there are workarounds, but they're difficult. Finally, Response.Redirect necessitates a round trip to the client, which, on high-volume sites, causes scalability problems. As you might suspect, Server.Transfer fixes all of these problems. It does this by performing the transfer on the server without requiring a roundtrip to the client. Response.Redirect sends a response to the client browser instructing it to request the second page. This requires a round-trip to the client, and the client initiates the Request for the second page. Server.Transfer transfers the process to the second page without making a round-trip to the client. It also transfers the HttpContext to the second page, enabling the second page access to all the values in the HttpContext of the first page.

Q 82. Can you create an app domain?

Ans :- Yes, We can create user app domain by calling on of the following overload static methods of the System.AppDomain class


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1. Public static AppDomain CreateDomain(String friendlyName) 2. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo) 3. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, AppDomainSetup info) 4. Public static AppDomain CreateDomain(String friendlyName, Evidence securityInfo, String appBasePath, String appRelativeSearchPath, bool shadowCopyFiles)

Q 83. What are the various security methods which IIS Provides apart from .NET ?

Ans :- The various security methods which IIS provides are

a) Authentication Modes b) IP Address and Domain Name Restriction c) DNS Lookups DNS Lookups d) The Network ID and Subnet Mask e) SSL

Q 84. What is Web Gardening? How would using it affect a design?

Ans :- The Web Garden Model The Web garden model is configurable through the section of the machine.config file. Notice that the section is the only configuration section that cannot be placed in an application-specific web.config file. This means that the Web garden mode applies to all applications running on the machine. However, by using the node in the machine.config source, you can adapt machine-wide settings on a per-application basis.

Two attributes in the section affect the Web garden model. They are webGarden and cpuMask. The webGarden attribute takes a Boolean value that indicates whether or not multiple worker processes (one per each affinitized CPU) have to be used. The attribute is set to false by default. The cpuMask attribute stores a DWORD value whose binary representation provides a bit mask for the CPUs that are eligible to run the ASP.NET worker process. The default value is -1 (0xFFFFFF), which means that all available CPUs can be used. The contents of the cpuMask attribute is ignored when the webGarden attribute is false. The cpuMask attribute also sets an upper bound to the number of copies of aspnet_wp.exe that are running.


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Web gardening enables multiple worker processes to run at the same time. However, you should note that all processes will have their own copy of application state, in-process session state, ASP.NET cache, static data, and all that is needed to run applications. When the Web garden mode is enabled, the ASP.NET ISAPI launches as many worker processes as there are CPUs, each a full clone of the next (and each affinitized with the corresponding CPU). To balance the workload, incoming requests are partitioned among running processes in a round-robin manner. Worker processes get recycled as in the single processor case. Note that ASP.NET inherits any CPU usage restriction from the operating system and doesn't include any custom semantics for doing this.

All in all, the Web garden model is not necessarily a big win for all applications. The more stateful applications are, the more they risk to pay in terms of real performance. Working data is stored in blocks of shared memory so that any changes entered by a process are immediately visible to others. However, for the time it takes to service a request, working data is copied in the context of the process. Each worker process, therefore, will handle its own copy of working data, and the more stateful the application, the higher the cost in performance. In this context, careful and savvy application benchmarking is an absolute must.

Changes made to the section of the configuration file are effective only after IIS is restarted. In IIS 6, Web gardening parameters are stored in the IIS metabase; the webGarden and cpuMask attributes are ignored.

Q 85. What is view state?.where it stored?.can we disable it?

Ans :- The web is state-less protocol, so the page gets instantiated, executed, rendered and then disposed on every round trip to the server. The developers code to add "statefulness" to the page by using Server-side storage for the state or posting the page to itself. When require to persist and read the data in control on webform, developer had to read the values and store them in hidden variable (in the form), which were then used to restore the values. With advent of .NET framework, ASP.NET came up with ViewState mechanism, which tracks the data values of server controls on ASP.NET webform. In effect,ViewState can be viewed as "hidden variable managed by ASP.NET framework!". When ASP.NET page is executed, data values from all server controls on page are collected and encoded as single string, which then assigned to page's hidden atrribute "< input type=hidden >", that is part of page sent to the client.


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ViewState value is temporarily saved in the client's browser.ViewState can be disabled for a single control, for an entire page orfor an entire web application. The syntax is:

Disable ViewState for control (Datagrid in this example) < asp:datagrid EnableViewState="false" ... / >

Disable ViewState for a page, using Page directive < %@ Page EnableViewState="False" ... % >

Disable ViewState for application through entry in web.config < Pages EnableViewState="false" ... / >


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Dot Net Framework FAQ�s Q 1. When was .NET announced? Ans :- Bill Gates delivered a keynote at Forum 2000, held June 22, 2000, outlining the .NET 'vision'. The July 2000 PDC had a number of sessions on .NET technology, and delegates were given CDs containing a pre-release version of the .NET framework/SDK and Visual Studio.NET. Q 2. When was the first version of .NET released? Ans :- The final version of the 1.0 SDK and runtime was made publicly available around 6pm PST on 15-Jan-2002. At the same time, the final version of Visual Studio.NET was made available to MSDN subscribers. Q 3. What platforms does the .NET Framework run on? Ans :- The runtime supports Windows XP, Windows 2000, NT4 SP6a and Windows ME/98. Windows 95 is not supported. Some parts of the framework do not work on all platforms - for example, ASP.NET is only supported on Windows XP and Windows 2000. Windows 98/ME cannot be used for development. IIS is not supported on Windows XP Home Edition, and so cannot be used to host ASP.NET. However, the ASP.NET Web Matrix web server does run on XP Home. The Mono project is attempting to implement the .NET framework on Linux. Q. 4 What is the CLR?


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Ans : CLR = Common Language Runtime. The CLR is a set of standard resources that (in theory) any .NET program can take advantage of, regardless of programming language. Robert Schmidt (Microsoft) lists the following CLR resources in his MSDN PDC# article: Object-oriented programming model (inheritance, polymorphism, exception handling, garbage collection) Security model Type system All .NET base classes Many .NET framework classes Development, debugging, and profiling tools Execution and code management IL-to-native translators and optimizers What this means is that in the .NET world, different programming languages will be more equal in capability than they have ever been before, although clearly not all languages will support all CLR services. Q 5. What is the CTS? Ans :- CTS = Common Type System. This is the range of types that the .NET runtime understands, and therefore that .NET applications can use. However note that not all .NET languages will support all the types in the CTS. The CTS is a superset of the CLS. Q 6. What is the CLS? Ans : -CLS = Common Language Specification. This is a subset of the CTS which all .NET languages are expected to support. The idea is that any program which uses CLS-compliant types can interoperate with any .NET program written in any language. In theory this allows very tight interop between different .NET languages - for example allowing a C# class to inherit from a VB class. Q 7. What is IL? Ans :- IL = Intermediate Language. Also known as MSIL (Microsoft Intermediate Language) or CIL (Common Intermediate Language). All .NET source code (of any language) is compiled to IL. The IL is then converted to machine code at the point where the software is installed, or at run-time by a Just-In-Time (JIT) compiler.


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Q 8. What does 'managed' mean in the .NET context? Ans :- The term 'managed' is the cause of much confusion. It is used in various places within .NET, meaning slightly different things.Managed code: The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. Such code is called managed code. All C# and Visual Basic.NET code is managed by default. VS7 C++ code is not managed by default, but the compiler can produce managed code by specifying a command-line switch (/com+). Managed data: This is data that is allocated and de-allocated by the .NET runtime's garbage collector. C# and VB.NET data is always managed. VS7 C++ data is unmanaged by default, even when using the /com+ switch, but it can be marked as managed using the __gc keyword.Managed classes: This is usually referred to in the context of Managed Extensions (ME) for C++. When using ME C++, a class can be marked with the __gc keyword. As the name suggests, this means that the memory for instances of the class is managed by the garbage collector, but it also means more than that. The class becomes a fully paid-up member of the .NET community with the benefits and restrictions that brings. An example of a benefit is proper interop with classes written in other languages - for example, a managed C++ class can inherit from a VB class. An example of a restriction is that a managed class can only inherit from one base class. Q 9. What is reflection? Ans :- All .NET compilers produce metadata about the types defined in the modules they produce. This metadata is packaged along with the module (modules in turn are packaged together in assemblies), and can be accessed by a mechanism called reflection. The System.Reflection namespace contains classes that can be used to interrogate the types for a module/assembly. Using reflection to access .NET metadata is very similar to using ITypeLib/ITypeInfo to access type library data in COM, and it is used for similar purposes - e.g. determining data type sizes for marshaling data across context/process/machine boundaries. Reflection can also be used to dynamically invoke methods (see System.Type.InvokeMember ) , or even create types dynamically at run-time (see System.Reflection.Emit.TypeBuilder). Q 10 . What is the difference between Finalize and Dispose (Garbage collection) ?


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Ans :- Class instances often encapsulate control over resources that are not managed by the runtime, such as window handles (HWND), database connections, and so on. Therefore, you should provide both an explicit and an implicit way to free those resources. Provide implicit control by implementing the protected Finalize Method on an object (destructor syntax in C# and the Managed Extensions for C++). The garbage collector calls this method at some point after there are no longer any valid references to the object. In some cases, you might want to provide programmers using an object with the ability to explicitly release these external resources before the garbage collector frees the object. If an external resource is scarce or expensive, better performance can be achieved if the programmer explicitly releases resources when they are no longer being used. To provide explicit control, implement the Dispose method provided by the IDisposable Interface. The consumer of the object should call this method when it is done using the object. Dispose can be called even if other references to the object are alive. Note that even when you provide explicit control by way of Dispose, you should provide implicit cleanup using the Finalize method. Finalize provides a backup to prevent resources from permanently leaking if the programmer fails to call Dispose. Q 11. What is Partial Assembly References? Ans :- Full Assembly reference: A full assembly reference includes the assembly's text name, version, culture, and public key token (if the assembly has a strong name). A full assembly reference is required if you reference any assembly that is part of the common language runtime or any assembly located in the global assembly cache. Partial Assembly reference: We can dynamically reference an assembly by providing only partial information, such as specifying only the assembly name. When you specify a partial assembly reference, the runtime looks for the assembly only in the application directory. We can make partial references to an assembly in your code one of the following ways: -> Use a method such as System.Reflection.Assembly.Load and specify only a partial reference. The runtime checks for the assembly in the application directory. -> Use the System.Reflection.Assembly.LoadWithPartialName method and specify only a partial reference. The runtime checks for the assembly in the application directory and in the global assembly cache


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Q 12. Changes to which portion of version number indicates an incompatible change? Ans :- Major or minor. Changes to the major or minor portion of the version number indicate an incompatible change. Under this convention then, version 2.0.0.0 would be considered incompatible with version 1.0.0.0. Examples of an incompatible change would be a change to the types of some method parameters or the removal of a type or method altogether. Build. The Build number is typically used to distinguish between daily builds or smaller compatible releases. Revision. Changes to the revision number are typically reserved for an incremental build needed to fix a particular bug. You'll sometimes hear this referred to as the "emergency bug fix" number in that the revision is what is often changed when a fix to a specific bug is shipped to a customer. Q 13. What is side-by-side execution? Can two application one using private assembly and other using Shared assembly be stated as a side-by-side executables? Ans :- Side-by-side execution is the ability to run multiple versions of an application or component on the same computer. You can have multiple versions of the common language runtime, and multiple versions of applications and components that use a version of the runtime, on the same computer at the same time. Since versioning is only applied to shared assemblies, and not to private assemblies, two application one using private assembly and one using shared assembly cannot be stated as side-by-side executables. Q 14. Why string are called Immutable data Type ? Ans : -The memory representation of string is an Array of Characters, So on re-assigning the new array of Char is formed & the start address is changed . Thus keeping the Old string in Memory for Garbage Collector to be disposed. Q 15. What does assert() method do? Ans :- In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.


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Q 16. What's the difference between the Debug class and Trace class? Ans :- Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds. Q 17. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? Ans :- The tracing dumps can be quite verbose. For applications that are constantly running you run the risk of overloading the machine and the hard drive. Five levels range from None to Verbose, allowing you to fine-tune the tracing activities. Q 18. Where is the output of TextWriterTraceListener redirected? Ans :- To the Console or a text file depending on the parameter passed to the constructor. Q 19. How do assemblies find each other? Ans ;- By searching directory paths. There are several factors which can affect the path (such as the AppDomain host, and application configuration files), but for private assemblies the search path is normally the application's directory and its sub-directories. For shared assemblies, the search path is normally same as the private assembly path plus the shared assembly cache. Q 20. How does assembly versioning work? Ans :- Each assembly has a version number called the compatibility version. Also each reference to an assembly (from another assembly) includes both the name and version of the referenced assembly.The version number has four numeric parts (e.g. 5.5.2.33). Assemblies with either of the first two parts different are normally viewed as incompatible. If the first two parts are the same, but the third is different, the assemblies are deemed as 'maybe compatible'. If only the fourth part is different, the assemblies are deemed compatible. However, this is just the default guideline - it is the version policy that decides to what extent these rules are enforced. The version policy can be specified via the application configuration file. Q 21. What is garbage collection? Ans :- Garbage collection is a system whereby a run-time component takes responsibility for managing the lifetime of objects and the heap memory that they


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occupy. This concept is not new to .NET - Java and many other languages/runtimes have used garbage collection for some time. Q 22. Why doesn't the .NET runtime offer deterministic destruction? Ans ;- Because of the garbage collection algorithm. The .NET garbage collector works by periodically running through a list of all the objects that are currently being referenced by an application. All the objects that it doesn't find during this search are ready to be destroyed and the memory reclaimed. The implication of this algorithm is that the runtime doesn't get notified immediately when the final reference on an object goes away - it only finds out during the next sweep of the heap. Futhermore, this type of algorithm works best by performing the garbage collection sweep as rarely as possible. Normally heap exhaustion is the trigger for a collection sweep. Q 23. Is the lack of deterministic destruction in .NET a problem? Ans :- It's certainly an issue that affects component design. If you have objects that maintain expensive or scarce resources (e.g. database locks), you need to provide some way for the client to tell the object to release the resource when it is done. Microsoft recommend that you provide a method called Dispose() for this purpose. However, this causes problems for distributed objects - in a distributed system who calls the Dispose() method? Some form of reference-counting or ownership-management mechanism is needed to handle distributed objects - unfortunately the runtime offers no help with this. Q 24. What is serialization? Ans :-Serialization is the process of converting an object into a stream of bytes. Deserialization is the opposite process of creating an object from a stream of bytes. Serialization / Deserialization is mostly used to transport objects (e.g. during remoting), or to persist objects (e.g. to a file or database). Q 25. In the .NET Framework have in-built support for serialization? Ans : - There are two separate mechanisms provided by the .NET class library - XmlSerializer and SoapFormatter/BinaryFormatter. Microsoft uses XmlSerializer


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for Web Services, and uses SoapFormatter/BinaryFormatter for remoting. Both are available for use in your own code. Q 26. Can I customise the serialization process? Ans :- Yes. XmlSerializer supports a range of attributes that can be used to configure serialization for a particular class. For example, a field or property can be marked with the [XmlIgnore] attribute to exclude it from serialization. Another example is the [XmlElement] attribute, which can be used to specify the XML element name to be used for a particular property or field. Serialization via SoapFormatter/BinaryFormatter can also be controlled to some extent by attributes. For example, the [NonSerialized] attribute is the equivalent of XmlSerializer's [XmlIgnore] attribute. Ultimate control of the serialization process can be acheived by implementing the the ISerializable interface on the class whose instances are to be serialized. Q 27. Why is XmlSerializer so slow? Ans :- There is a once-per-process-per-type overhead with XmlSerializer. So the first time you serialize or deserialize an object of a given type in an application, there is a significant delay. This normally doesn't matter, but it may mean, for example, that XmlSerializer is a poor choice for loading configuration settings during startup of a GUI application. Q 28. Why do I get errors when I try to serialize a Hashtable? Ans :- XmlSerializer will refuse to serialize instances of any class that implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction. Q 29. What are attributes? Ans :- There are at least two types of .NET attribute. The first type I will refer to as a metadata attribute - it allows some data to be attached to a class or method. This data becomes part of the metadata for the class, and (like other class metadata) can be accessed via reflection. The other type of attribute is a context attribute. Context attributes use a similar syntax to metadata attributes but they are fundamentally different. Context


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attributes provide an interception mechanism whereby instance activation and method calls can be pre- and/or post-processed. Q 30. How does CAS work? Ans :- The CAS security policy revolves around two key concepts - code groups and permissions. Each .NET assembly is a member of a particular code group, and each code group is granted the permissions specified in a named permission set. For example, using the default security policy, a control downloaded from a web site belongs to the 'Zone - Internet' code group, which adheres to the permissions defined by the 'Internet' named permission set. (Naturally the 'Internet' named permission set represents a very restrictive range of permissions.) Q 31. Who defines the CAS code groups? Ans :- Microsoft defines some default ones, but you can modify these and even create your own. To see the code groups defined on your system, run 'caspol -lg' from the command-line. On my system it looks like this: Level = Machine Code Groups: 1. All code: Nothing 1.1. Zone - MyComputer: FullTrust 1.1.1. Honor SkipVerification requests: SkipVerification 1.2. Zone - Intranet: LocalIntranet 1.3. Zone - Internet: Internet 1.4. Zone - Untrusted: Nothing 1.5. Zone - Trusted: Internet 1.6. StrongName - 0024000004800000940000000602000000240000525341310004000003 000000CFCB3291AA715FE99D40D49040336F9056D7886FED46775BC7BB5430BA4444FEF8348EBD06 F962F39776AE4DC3B7B04A7FE6F49F25F740423EBF2C0B89698D8D08AC48D69CED0FC8F83B465E08 07AC11EC1DCC7D054E807A43336DDE408A5393A48556123272CEEEE72F1660B71927D38561AABF5C AC1DF1734633C602F8F2D5: Note the hierarchy of code groups - the top of the hierarchy is the most general ('All code'), which is then sub-divided into several


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groups, each of which in turn can be sub-divided. Also note that (somewhat counter-intuitively) a sub-group can be associated with a more permissive permission set than its parent. Q 32.How do I define my own code group? Ans :- Use caspol. For example, suppose you trust code from www.mydomain.com and you want it have full access to your system, but you want to keep the default restrictions for all other internet sites. To achieve this, you would add a new code group as a sub-group of the 'Zone - Internet' group, like this: caspol -ag 1.3 -site www.mydomain.com FullTrust Now if you run caspol -lg you will see that the new group has been added as group 1.3.1: 1.3. Zone - Internet: Internet 1.3.1. Site - www.mydomain.com: FullTrust Note that the numeric label (1.3.1) is just a caspol invention to make the code groups easy to manipulate from the command-line. The underlying runtime never sees it. Q 33.How do I change the permission set for a code group? Ans :- Use caspol. If you are the machine administrator, you can operate at the 'machine' level - which means not only that the changes you make become the default for the machine, but also that users cannot change the permissions to be more permissive. If you are a normal (non-admin) user you can still modify the permissions, but only to make them more restrictive. For example, to allow intranet code to do what it likes you might do this: caspol -cg 1.2 FullTrust Note that because this is more permissive than the default policy (on a standard system), you should only do this at the machine level - doing it at the user level will have no effect. Q 34. I can't be bothered with all this CAS stuff. Can I turn it off? Ans :- Yes, as long as you are an administrator. Just run: caspol -s off Q 35.Can I look at the IL for an assembly?


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Ans ;- Yes. MS supply a tool called Ildasm which can be used to view the metadata and IL for an assembly. Q 36.Can source code be reverse-engineered from IL? Ans :- Yes, it is often relatively straightforward to regenerate high-level source (e.g. C#) from IL. Q 37. How can I stop my code being reverse-engineered from IL? Ans :- There is currently no simple way to stop code being reverse-engineered from IL. In future it is likely that IL obfuscation tools will become available, either from MS or from third parties. These tools work by 'optimising' the IL in such a way that reverse-engineering becomes much more difficult. Of course if you are writing web services then reverse-engineering is not a problem as clients do not have access to your IL. Q 38. Is there built-in support for tracing/logging? Ans :- Yes, in the System.Diagnostics namespace. There are two main classes that deal with tracing - Debug and Trace. They both work in a similar way - the difference is that tracing from the Debug class only works in builds that have the DEBUG symbol defined, whereas tracing from the Trace class only works in builds that have the TRACE symbol defined. Typically this means that you should use System.Diagnostics.Trace.WriteLine for tracing that you want to work in debug and release builds, and System.Diagnostics.Debug.WriteLine for tracing that you want to work only in debug builds. Q 39. Can I redirect tracing to a file? Ans :- Yes. The Debug and Trace classes both have a Listeners property, which is a collection of sinks that receive the tracing that you send via Debug.WriteLine and Trace.WriteLine respectively. By default the Listeners collection contains a single sink, which is an instance of the DefaultTraceListener class. This sends output to the Win32 OutputDebugString() function and also the System.Diagnostics.Debugger.Log() method. This is useful when debugging, but if you're trying to trace a problem at a customer site, redirecting the output to a file is more appropriate. Fortunately, the TextWriterTraceListener class is provided for this purpose.


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Q 40. What are the contents of assembly? Ans :- In general, a static assembly can consist of four elements: The assembly manifest, which contains assembly metadata. Type metadata. Microsoft intermediate language (MSIL) code that implements the types. A set of resources. Q 41. What is GC (Garbage Collection) and how it works? Ans :- One of the good features of the CLR is Garbage Collection, which runs in the background collecting unused object references, freeing us from having to ensure we always destroy them. In reality the time difference between you releasing the object instance and it being garbage collected is likely to be very small, since the GC is always running. [The process of transitively tracing through all pointers to actively used objects in order to locate all objects that can be referenced, and then arranging to reuse any heap memory that was not found during this trace. The common language runtime garbage collector also compacts the memory that is in use to reduce the working space needed for the heap.] Heap: A portion of memory reserved for a program to use for the temporary storage of data structures whose existence or size cannot be determined until the program is running. Q 42. Differnce between Managed code and unmanaged code ? Ans :- Managed Code: Code that runs under a "contract of cooperation" with the common language runtime. Managed code must supply the metadata necessary for the runtime to provide services such as memory management, cross-language integration, code access security, and automatic lifetime control of objects. All code based on Microsoft intermediate language (MSIL) executes as managed code. Un-Managed Code:


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Code that is created without regard for the conventions and requirements of the common language runtime. Unmanaged code executes in the common language runtime environment with minimal services (for example, no garbage collection, limited debugging, and so on). Q 43. What is MSIL, IL, CTS and, CLR ? Ans ;- MSIL: (Microsoft intermediate language) When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be executed, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and executed on any supported architecture. When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of each type, the signatures of each type's members, the members that your code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and Common Object File Format (COFF) used historically for executable content. This file format, which accommodates MSIL or native code as well as metadata, enables the operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution. IL: (Intermediate Language) A language used as the output of a number of compilers and as the input to a just-in-time (JIT) compiler. The common language runtime includes a JIT compiler for converting MSIL to native code.


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CTS: (Common Type System) The specification that determines how the common language runtime defines, uses, and manages types CLR: (Common Language Runtime) The engine at the core of managed code execution. The runtime supplies managed code with services such as cross-language integration, code access security, object lifetime management, and debugging and profiling support. Q 44. What is Reference type and value type ? Ans :- Reference Type: Reference types are allocated on the managed CLR heap, just like object types. A data type that is stored as a reference to the value's location. The value of a reference type is the location of the sequence of bits that represent the type's data. Reference types can be self-describing types, pointer types, or interface types Value Type: Value types are allocated on the stack just like primitive types in VBScript, VB6 and C/C++. Value types are not instantiated using new go out of scope when the function they are defined within returns. Value types in the CLR are defined as types that derive from system.valueType. A data type that fully describes a value by specifying the sequence of bits that constitutes the value's representation. Type information for a value type instance is not stored with the instance at run time, but it is available in metadata. Value type instances can be treated as objects using boxing. Q 45.What is Boxing and unboxing ? Ans :- Boxing: The conversion of a value type instance to an object, which implies that the instance will carry full type information at run time and will be allocated in the heap. The Microsoft intermediate language (MSIL) instruction set's box instruction converts a value type to an object by making a copy of the value type and embedding it in a newly allocated object.


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Un-Boxing: The conversion of an object instance to a value type. Q 46. What is JIT and how is works ? Ans :- An acronym for "just-in-time," a phrase that describes an action that is taken only when it becomes necessary, such as just-in-time compilation or just-in-time object activation Q 47.What is portable executable (PE) ? Ans ;- The file format used for executable programs and for files to be linked together to form executable programs Q 48. What is strong name? Ans :- A name that consists of an assembly's identity�its simple text name, version number, and culture information (if provided)�strengthened by a public key and a digital signature generated over the assembly. Because the assembly manifest contains file hashes for all the files that constitute the assembly implementation, it is sufficient to generate the digital signature over just the one file in the assembly that contains the assembly manifest. Assemblies with the same strong name are expected to be identical Q 49. What is global assembly cache? Ans :- A machine-wide code cache that stores assemblies specifically installed to be shared by many applications on the computer. Applications deployed in the global assembly cache must have a strong name. Q 50. What is difference between constants, readonly and, static ? Ans ;- Constants: The value can�t be changed Read-only: The value will be initialized only once from the constructor of the class. Static: Value can be initialized once. Q 51. What is difference between shared and public? Ans :- An assembly that can be referenced by more than one application. An


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assembly must be explicitly built to be shared by giving it a cryptographically strong name. Q 52. What is namespace used for loading assemblies at run time and name the methods? Ans:- System.Reflection Q 53. What are the types of authentication in .net? Ans :- We have three types of authentication: 1. Form authentication 2. Windows authentication 3. Passport This has to be declared in web.config file. Q 54. What is the difference between a Struct and a Class ? Ans :- The struct type is suitable for representing lightweight objects such as Point, Rectangle, and Color. Although it is possible to represent a point as a class, a struct is more efficient in some scenarios. For example, if you declare an array of 1000 Point objects, you will allocate additional memory for referencing each object. In this case, the struct is less expensive. When you create a struct object using the new operator, it gets created and the appropriate constructor is called. Unlike classes, structs can be instantiated without using the new operator. If you do not use new, the fields will remain unassigned and the object cannot be used until all of the fields are initialized. It is an error to declare a default (parameterless) constructor for a struct. A default constructor is always provided to initialize the struct members to their default values. It is an error to initialize an instance field in a struct. There is no inheritance for structs as there is for classes. A struct cannot inherit from another struct or class, and it cannot be the base of a class. Structs, however, inherit from the base class Object. A struct can implement interfaces, and it does that exactly as classes do. A struct is a value type, while a class is a reference type. Q 55. How big is the datatype int in .NET? Ans ;- 32 bits.


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Q 56. How big is the char? Ans:- 6 bits (Unicode). Q 57. How do you initiate a string without escaping each backslash? Ans :- Put an @ sign in front of the double-quoted string. Q 58. What's the access level of the visibility type internal? Ans :- Current application. Q 59. Explain encapsulation ? Ans:- The implementation is hidden, the interface is exposed. Q 60. What data type should you use if you want an 8-bit value that's signed? Ans :- sbyte. Q 61. Speaking of Boolean data types, what's different between C# and C/C++? Ans :-There's no conversion between 0 and false, as well as any other number and true, like in C/C++ . Q 62. Where are the value-type variables allocated in the computer RAM? Ans :- Stack. Q 63.Where do the reference-type variables go in the RAM? Ans :- The references go on the stack, while the objects themselves go on the heap. Q 64. What is the difference between the value-type variables and reference-type variables in terms of garbage collection? Ans:- The value-type variables are not garbage-collected, they just fall off the stack when they fall out of scope, the reference-type objects


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are picked up by GC when their references go null. Q 65. How do you convert a string into an integer in .NET? Ans :- Int32.Parse(string) Q 66. How do you box a primitive data type variable? Ans :- Assign it to the object, pass an object. Q 67. Why do you need to box a primitive variable? Ans :- To pass it by reference. Q 68. What's the difference between Java and .NET garbage collectors? Ans :- Sun left the implementation of a specific garbage collector up to the JRE developer, so their performance varies widely, depending on whose JRE you're using. Microsoft standardized on their garbage collection. Q 69. How do you enforce garbage collection in .NET? Ans:- System.GC.Collect(); Q 70. What's different about namespace declaration when comparing that to package Ans :- declaration in Java? No semicolon. Q 71. What's the difference between const and readonly? Ans :- You can initialize readonly variables to some runtime values. Let's say your program uses current date and time as one of the values that won't change. This way you declare public readonly string DateT = new DateTime().ToString(). Q 72. What happens when you encounter a continue statement inside the for loop?


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Ans :- The code for the rest of the loop is ignored, the control is transferred back to the beginning of the loop. Q 73. What's the advantage of using System.Text.StringBuilder over System.String? Ans :- StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it's being operated on, a new instance is created. Q 74. Can you store multiple data types in System.Array? Ans :- No. Q 75. What's the difference between the System.Array.CopyTo() and System.Array.Clone()? Ans :- The first one performs a deep copy of the array, the second one is shallow. Q 76. How can you sort the elements of the array in descending order? Ans :- By calling Sort() and then Reverse() methods. Q 77. What's the .NET datatype that allows the retrieval of data by a unique key? Ans :- HashTable. Q 78. What's class SortedList underneath? Ans ;- A sorted HashTable. Q 79. Will finally block get executed if the exception had not occurred? Ans :- Yes. Q 80. Can multiple catch blocks be executed?


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Ans :- No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block. Q 81. Why is it a bad idea to throw your own exceptions? Ans:- Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project. Q 82. What's a delegate? Ans :- A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers. Q 83. What's a multicast delegate? Ans:- It's a delegate that points to and eventually fires off several methods. Q 84. How's the DLL Hell problem solved in .NET? Ans :- Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly. Q 85. What are the ways to deploy an assembly? Ans :- An MSI installer, a CAB archive, and XCOPY command. Q 86. What's a satellite assembly? Ans :- When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies. Q 87. What namespaces are necessary to create a localized application? Ans :--System.Globalization, System.Resources.


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Q 88. What does assert() do? Ans:- In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true. Q 89. What's the difference between the Debug class and Trace class? Ans :- Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds. Q 90. Why are there five tracing levels in System.Diagnostics.TraceSwitcher? Ans :- The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities. Q 91. Where is the output of TextWriterTraceListener redirected? Ans :- To the Console or a text file depending on the parameter passed to the constructor. Q 92. What namespaces are necessary to create a localized application? Ans:- System.Globalization, System.Resources. Q 93.What are three test cases you should go through in unit testing? Ans :- Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly). Q 94. Can you change the value of a variable while debugging a C# application? Ans :- Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.


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Q 95 .What's the implicit name of the parameter that gets passed into the class' set method? Ans :- Value, and it's datatype depends on whatever variable we're changing. Q 96. How do you inherit from a class in C#? Ans :- Place a colon and then the name of the base class. Notice that it's double colon in C++. Q 97. Does C# support multiple inheritance? Ans :- No, use interfaces instead. Q 98. When you inherit a protected class-level variable, who is it available to? Ans :- Derived Classes. Q 99. What's the top .NET class that everything is derived from? Ans :- System.Object. Q 100. How's method overriding different from overloading? Ans:- When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class. Q 101. What does the keyword virtual mean in the method definition? Ans :- The method can be over-ridden. Q 102. Can you declare the override method static while the original method is non-static? Ans :- No, you can't, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override. Q 103. Can you override private virtual methods?


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Ans :- No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access. Q 104. Can you prevent your class from being inherited and becoming a base class for some other classes? Ans :- Yes, that's what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It's the same concept as final class in Java. Q 105. Can you allow class to be inherited, but prevent the method from being over-ridden? Ans :- Yes, just leave the class public and make the method sealed. Q 106. Why can't you specify the accessibility modifier for methods inside the interface? Ans :- They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it's public by default. Q 107. Can you inherit multiple interfaces? Ans :- Yes, why not. Q 108. And if they have conflicting method names? Ans :- It's up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you're okay. Q 109. What's the difference between an interface and abstract class? Ans :- In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.


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Q 110. How can you overload a method? Ans :- Different parameter data types, different number of parameters, different order of parameters. Q 111. If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Ans:- Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class. Q 112. What's the difference between System.String and System.StringBuilder classes? Ans :- System.String is immutable, System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed. Q 113. Does C# support multiple-inheritance? Ans:- No, use interfaces instead. Q 113. When you inherit a protected class-level variable, who is it available to? Ans :- The derived class. Q 114. Are private class-level variables inherited? Ans :- Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited. Q 115. Describe the accessibility modifier "protected internal". Ans :- It is available to derived classes and classes within the same Assembly (and naturally from the base class it's declared in). Q 116. What's the top .NET class that everything is derived from?


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Ans :- System.Object. Q 117. What's the advantage of using System.Text.StringBuilder over System.String? Ans :- StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time it's being operated on, a new instance is created. Q 118. Can you store multiple data types in System.Array? Ans :- No. Q 119. What's the .NET class that allows the retrieval of a data element using a unique key? Ans:- HashTable. Q 120. Will the finally block get executed if an exception has not occurred? Ans :- Yes. Q 121. What's an abstract class? Ans :- A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation. Q 122. When do you absolutely have to declare a class as abstract? Ans :- 1. When at least one of the methods in the class is abstract. 2. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden. Q 123. What's an interface?


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Ans :- It's an abstract class with public abstract methods all of which must be implemented in the inherited classes. Q 124. Why can't you specify the accessibility modifier for methods inside the interface? Ans :- They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it's public by default. Q 125.What's the difference between an interface and abstract class? Ans :- In an Interface class, all methods must be abstract. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed, which is ok in an abstract class. Q 126. How is method overriding different from method overloading? Ans :- When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class. Q127. Can you declare an override method to be static if the original method is non- static? Ans :- No. The signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override. Q 128. Can you override private virtual methods? Ans :- No. Private methods are not accessible outside the class. Q 129. Can you write a class without specifying namespace? Which namespace does it belong to by default? Ans :- Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you wouldn't want global namespace. Q 130. What is a formatter?


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Ans :- A formatter is an object that is responsible for encoding and serializing data into messages on one end, and deserializing and decoding messages into data on the other end.

Q 131. Different b/w .NET & J2EE ?

Ans: - Differences between J2EE and the .NET Platform

Vendor Neutrality

The .NET platform is not vendor neutral, it is tied to the Microsoft operating systems. But neither are any of the J2EE implementations Many companies buy into J2EE believing that it will give them vendor neutrality. And, in fact, this is a stated goal of Sun's vision: A wide variety of J2EE product configurations and implementations, all of which meet the requirements of this specification, are possible. A portable J2EE application will function correctly when successfully deployed in any of these products. (ref : Java 2 Platform Enterprise Edition Specification, v1.3, page 2-7 available at http://java.sun.com/j2ee/)

Overall Maturity

Given that the .NET platform has a three year lead over J2EE, it should be no surprise to learn that the .NET platform is far more mature than the J2EE platform. Whereas we have high volume highly reliable web sites using .NET technologies (NASDAQ and Dell being among many examples)

Interoperability and Web Services

The .NET platform eCollaboration model is, as I have discussed at length, based on the UDDI and SOAP standards. These standards are widely supported by more than 100 companies. Microsoft, along with IBM and Ariba, are the leaders in this area. Sun is a member of the UDDI consortium and recognizes the importance of the UDDI standards. In a recent press release, Sun's George Paolini, Vice President for the Java Community Development, says:

"Sun has always worked to help establish and support open, standards-based technologies that facilitate the growth of network-based applications, and we see


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UDDI as an important project to establish a registry framework for business-to-business e-commerce

But while Sun publicly says it believes in the UDDI standards, in reality, Sun has done nothing whatsoever to incorporate any of the UDDI standards into J2EE.

Scalability

Typical Comparision w.r.t Systems and their costs

J2EE

Company System Total Sys. Cost Bull Escala T610 c/s 16,785 $1,980,179 IBM RS/6000 Enterprise Server F80 16,785 $2,026,681 Bull Escala EPC810 c/s 33,375 $3,037,499 IBM RS/6000 Enterprise Server M80 33,375 $3,097,055 Bull Escala EPC2450 110,403 $9,563,263 IBM IBM eServer pSeries 680 Model 7017-S85 110,403 $9,560,594

.NET platform systems

Company System Total Sys. Cost Dell PowerEdge 4400 16,263 $273,487 Compaq ProLiant ML-570-6/700-3P 20,207 $201,717 Dell PowerEdge 6400 30,231 $334,626 IBM Netfinity 7600 c/s 32,377 $443,463 Compaq ProLiant 8500-X550-64P 161,720 $3,534,272 Compaq ProLiant 8500-X700-64P 179,658 $3,546,582 Compaq ProLiant 8500-X550-96P 229,914 $5,305,571 Compaq ProLiant 8500-X700-96P 262,244 $5,305,571 Compaq ProLiant 8500-700-192P 505,303 $10,003,826

Framework Support

The .NET platform includes such an eCommerce framework called Commerce Server. At this point, there is no equivalent vendor-neutral framework in the J2EE


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space. With J2EE, you should assume that you will be building your new eCommerce solution from scratch

Moreover, no matter what [J2EE] vendor you choose, if you expect a component framework that will allow you to quickly field complete e-business applications, you are in for a frustrating experience

Language

In the language arena, the choice is about as simple as it gets. J2EE supports Java, and only Java. It will not support any other language in the foreseeable future. The .NET platform supports every language except Java (although it does support a language that is syntactically and functionally equivalent to Java, C#). In fact, given the importance of the .NET platform as a language independent vehicle, it is likely that any language that comes out in the near future will include support for the .NET platform.

Some companies are under the impression that J2EE supports other languages. Although both IBM's WebSphere and BEA's WebLogic support other languages, neither does it through their J2EE technology. There are only two official ways in the J2EE platform to access other languages, one through the Java Native Interface and the other through CORBA interoperability. Sun recommends the later approach. As Sun's Distinguished Scientist and Java Architect Rick Cattell said in a recent interview.

Portability

The reason that operating system portability is a possibility with J2EE is not so much because of any inherent portability of J2EE, as it is that most of the J2EE vendors support multiple operating systems. Therefore as long as one sticks with a given J2EE vendor and a given database vendor, moving from one operating system to another should be possible. This is probably the single most important benefit in favor of J2EE over the .NET platform, which is limited to the Windows operating system. It is worth noting, however, that Microsoft has submitted the specifications for C# and a subset of the .NET Framework (called the common language infrastructure) to ECMA, the group that standardizes JavaScript.

J2EE offers an acceptable solution to ISVs when the product must be marketed to non-Windows customers, particularly when the J2EE platform itself can be bundled with the ISV's product as an integrated offering.


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If the primary customer base for the ISV is Windows customers, then the .NET platform should be chosen. It will provide much better performance at a much lower cost.

Client device independence

The major difference being that with Java, it is the presentation tier programmer that determines the ultimate HTML that will be delivered to the client, and with .NET, it is a Visual Studio.NET control.

This Java approach has three problems. First, it requires a lot of code on the presentation tier, since every possible thin client system requires a different code path. Second, it is very difficult to test the code with every possible thin client system. Third, it is very difficult to add new thin clients to an existing application, since to do so involves searching through, and modifying a tremendous amount of presentation tier logic.

The .NET Framework approach is to write device independent code that interacts with visual controls. It is the control, not the programmer, that is responsible for determining what HTML to deliver, based on the capabilities of the client device.. In the .NET Framework model, one can forget that such a thing as HTML even exists! Contd .... Conclusion

Sun's J2EE vision is based on a family of specifications that can be implemented by many vendors. It is open in the sense that any company can license and implement the technology, but closed in the sense that it is controlled by a single vendor, and a self contained architectural island with very limited ability to interact outside of itself. One of J2EE's major disadvantages is that the choice of the platform dictates the use of a single programming language, and a programming language that is not well suited for most businesses. One of J2EE's major advantages is that most of the J2EE vendors do offer operating system portability.

Microsoft's .NET platform vision is a family of products rather than specifications, with specifications used primarily to define points of interoperability. The major disadvantage of this approach is that if is limited to the Windows platform, so applications written for the .NET platform can only be run on .NET platforms. Their are several important advantages to the .NET platform:


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* The cost of developing applications is much lower, since standard business languages can be used and device independent presentation tier logic can be written.

* The cost of running applications is much lower, since commodity hardware platforms (at 1/5 the cost of their Unix counterparts) can be used.

* The ability to scale up is much greater, with the proved ability to support at least ten times the number of clients any J2EE platform has shown itself able to support.

* Interoperability is much stronger, with industry standard eCollaboration built into the platform.

Q 132. What are the Main Features of .NET platform?

Ans :- Features of .NET Platform are :-

Common Language Runtime Explains the features and benefits of the common language runtime, a run-time environment that manages the execution of code and provides services that simplify the development process.

Assemblies Defines the concept of assemblies, which are collections of types and resources that form logical units of functionality. Assemblies are the fundamental units of deployment, version control, reuse, activation scoping, and security permissions.

Application Domains Explains how to use application domains to provide isolation between applications.

Runtime Hosts Describes the runtime hosts supported by the .NET Framework, including ASP.NET, Internet Explorer, and shell executables.

Common Type System Identifies the types supported by the common language runtime.

Metadata and Self-Describing Components Explains how the .NET Framework simplifies component interoperation by allowing compilers to emit additional declarative information, or metadata, into all modules and assemblies.


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Cross-Language Interoperability Explains how managed objects created in different programming languages can interact with one another.

.NET Framework Security Describes mechanisms for protecting resources and code from unauthorized code and unauthorized users.

.NET Framework Class Library Introduces the library of types provided by the .NET Framework, which expedites and optimizes the development process and gives you access to system functionality.

Q 133. What is the use of JIT ?

Ans :- JIT (Just - In - Time) is a compiler which converts MSIL code to Native Code (ie.. CPU-specific code that runs on the same computer architecture).

Because the common language runtime supplies a JIT compiler for each supported CPU architecture, developers can write a set of MSIL that can be JIT-compiled and run on computers with different architectures. However, your managed code will run only on a specific operating system if it calls platform-specific native APIs, or a platform-specific class library.

JIT compilation takes into account the fact that some code might never get called during execution. Rather than using time and memory to convert all the MSIL in a portable executable (PE) file to native code, it converts the MSIL as needed during execution and stores the resulting native code so that it is accessible for subsequent calls. The loader creates and attaches a stub to each of a type's methods when the type is loaded. On the initial call to the method, the stub passes control to the JIT compiler, which converts the MSIL for that method into native code and modifies the stub to direct execution to the location of the native code. Subsequent calls of the JIT-compiled method proceed directly to the native code that was previously generated, reducing the time it takes to JIT-compile and run the code.

Q 134. What meant of assembly & global assembly cache (gac) & Meta data.

Ans :- Assembly :-- An assembly is the primary building block of a .NET based application. It is a collection of functionality that is built, versioned, and deployed as a single implementation unit (as one or more files). All managed types and resources are marked either as accessible only within their implementation unit, or as


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accessible by code outside that unit. It overcomes the problem of 'dll Hell'.The .NET Framework uses assemblies as the fundamental unit for several purposes:

• Security

• Type Identity

• Reference Scope

• Versioning

• Deployment

Global Assembly Cache :-- Assemblies can be shared among multiple applications on the machine by registering them in global Assembly cache(GAC). GAC is a machine wide a local cache of assemblies maintained by the .NET Framework. We can register the assembly to global assembly cache by using gacutil command. We can Navigate to the GAC directory, C:\winnt\Assembly in explore. In the tools menu select the cache properties; in the windows displayed you can set the memory limit in MB used by the GAC MetaData :--Assemblies have Manifests. This Manifest contains Metadata information of the Module/Assembly as well as it contains detailed Metadata of other assemblies/modules references (exported). It's the Assembly Manifest which differentiates between an Assembly and a Module.

Q 135. What are the mobile devices supported by .net platform

Ans :- The Microsoft .NET Compact Framework is designed to run on mobile devices such as mobile phones, Personal Digital Assistants (PDAs), and embedded devices. The easiest way to develop and test a Smart Device Application is to use an emulator.

These devices are divided into two main divisions: 1) Those that are directly supported by .NET (Pocket PCs, i-Mode phones, and WAP devices) 2) Those that are not (Palm OS and J2ME-powered devices).

Q 136. What is GUID , why we use it and where?


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Ans :- GUID :-- GUID is Short form of Globally Unique Identifier, a unique 128-bit number that is produced by the Windows OS or by some Windows applications to identify a particular component, application, file, database entry, and/or user. For instance, a Web site may generate a GUID and assign it to a user's browser to record and track the session. A GUID is also used in a Windows registry to identify COM DLLs. Knowing where to look in the registry and having the correct GUID yields a lot information about a COM object (i.e., information in the type library, its physical location, etc.). Windows also identifies user accounts by a username (computer/domain and username) and assigns it a GUID. Some database administrators even will use GUIDs as primary key values in databases.

GUIDs can be created in a number of ways, but usually they are a combination of a few unique settings based on specific point in time (e.g., an IP address, network MAC address, clock date/time, etc.).

Q 137. Describe the difference between inline and code behind - which is best in a loosely coupled solution?

Ans :- ASP.NET supports two modes of page development: Page logic code that is written inside runat="server"> blocks within an .aspx file and dynamically compiled the first time the page is requested on the server. Page logic code that is written within an external class that is compiled prior to deployment on a server and linked ""behind"" the .aspx file at run time.

Q 138. Whats MSIL, and why should my developers need an appreciation of it if at all?

Ans :- When compiling the source code to managed code, the compiler translates the source into Microsoft intermediate language (MSIL). This is a CPU-independent set of instructions that can efficiently be converted to native code. Microsoft intermediate language (MSIL) is a translation used as the output of a number of compilers. It is the input to a just-in-time (JIT) compiler. The Common Language Runtime includes a JIT compiler for the conversion of MSIL to native code.

Before Microsoft Intermediate Language (MSIL) can be executed it, must be converted by the .NET Framework just-in-time (JIT) compiler to native code. This is CPU-specific code that runs on the same computer architecture as the JIT compiler. Rather than using time and memory to convert all of the MSIL in a portable


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executable (PE) file to native code. It converts the MSIL as needed whilst executing, then caches the resulting native code so its accessible for any subsequent calls.

Q 139. </SCRIPT>How many .NET languages can a single .NET DLL contain?

Ans :- One


Ans :- Server

Q 141. Whats an assembly?

Ans :- Assemblies are the building blocks of .NET Framework applications; they form the fundamental unit of deployment, version control, reuse, activation scoping, and security permissions. An assembly is a collection of types and resources that are built to work together and form a logical unit of functionality. An assembly provides the common language runtime with the information it needs to be aware of type implementations. To the runtime, a type does not exist outside the context of an assembly.

Q 142. How many classes can a single .NET DLL contain?

Ans :- Unlimited.

Q 143. What is the difference between string and String ?

Ans :- No difference

Q 144. What is manifest?

Ans :- It is the metadata that describes the assemblies.

Q 145. What is metadata?


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Ans :- Metadata is machine-readable information about a resource, or ""data about data."" Such information might include details on content, format, size, or other characteristics of a data source. In .NET, metadata includes type definitions, version information, external assembly references, and other standardized information.

Q 146. What are the types of assemblies?

Ans :- There are four types of assemblies in .NET:

Static assemblies These are the .NET PE files that you create at compile time.

Dynamic assemblies These are PE-formatted, in-memory assemblies that you dynamically create at runtime using the classes in the System.Reflection.Emit namespace.

Private assemblies These are static assemblies used by a specific application.

Public or shared assemblies These are static assemblies that must have a unique shared name and can be used by any application.

An application uses a private assembly by referring to the assembly using a static path or through an XML-based application configuration file. While the CLR doesn't enforce versioning policies-checking whether the correct version is used-for private assemblies, it ensures that an application uses the correct shared assemblies with which the application was built. Thus, an application uses a specific shared assembly by referring to the specific shared assembly, and the CLR ensures that the correct version is loaded at runtime.

In .NET, an assembly is the smallest unit to which you can associate a version number;

Q 147. What are delegates?where are they used ?

Ans :- A delegate defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance


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method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure.

Q 148. When do you use virutal keyword?.

Ans :- When we need to override a method of the base class in the sub class, then we give the virtual keyword in the base class method. This makes the method in the base class to be overridable. Methods, properties, and indexers can be virtual, which means that their implementation can be overridden in derived classes.

Q 149. What are class access modifiers ?

Ans :- Access modifiers are keywords used to specify the declared accessibility of a member or a type. This section introduces the four access modifiers: · Public - Access is not restricted. · Protected - Access is limited to the containing class or types derived from the containing class. · Internal - Access is limited to the current assembly. · Protected inertnal - Access is limited to the current assembly or types derived · from the containing class. · Private - Access is limited to the containing type.

Q 150. What Is Boxing And Unboxing?

Ans :- Boxing :- Boxing is an implicit conversion of a value type to the type object type

Eg:- Consider the following declaration of a value-type variable: int i = 123; object o = (object) i; Boxing Conversion

UnBoxing :- Unboxing is an explicit conversion from the type object to a value type Eg: int i = 123; // A value type


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object box = i; // Boxing int j = (int)box; // Unboxing

Q 151. What is Value type and refernce type in .Net?.

Ans :- Value Type : A variable of a value type always contains a value of that type. The assignment to a variable of a value type creates a copy of the assigned value, while the assignment to a variable of a reference type creates a copy of the reference but not of the referenced object.

The value types consist of two main categories: * Stuct Type * Enumeration Type

Reference Type :Variables of reference types, referred to as objects, store references to the actual data. This section introduces the following keywords used to declare reference types: * Class * Interface * Delegate

This section also introduces the following built-in reference types: * object * string

Q 152. What is the difference between structures and enumeration?.

Ans :- Unlike classes, structs are value types and do not require heap allocation. A variable of a struct type directly contains the data of the struct, whereas a variable of a class type contains a reference to the data. They are derived from System.ValueType class.

Enum->An enum type is a distinct type that declares a set of named constants.They are strongly typed constants. They are unique types that allow to declare symbolic names to integral values. Enums are value types, which means they contain their own value, can't inherit or be inherited from and assignment copies the value of one enum to another.


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public enum Grade { A, B, C }

Q 153. What is namespaces?.

Ans :- Namespace is a logical naming scheme for group related types.Some class types that logically belong together they can be put into a common namespace. They prevent namespace collisions and they provide scoping. They are imported as "using" in C# or "Imports" in Visual Basic. It seems as if these directives specify a particular assembly, but they don't. A namespace can span multiple assemblies, and an assembly can define multiple namespaces. When the compiler needs the definition for a class type, it tracks through each of the different imported namespaces to the type name and searches each referenced assembly until it is found. Namespaces can be nested. This is very similar to packages in Java as far as scoping is concerned.

Q 154. How do you create shared assemblies?.

Ans :- Just look through the definition of Assemblies.. * An Assembly is a logical unit of code * Assembly physically exist as DLLs or EXEs * One assembly can contain one or more files * The constituent files can include any file types like image files, text files etc. along with DLLs or EXEs * When you compile your source code by default the exe/dll generated is actually an assembly * Unless your code is bundled as assembly it can not be used in any other application * When you talk about version of a component you are actually talking about version of the assembly to which the component belongs. * Every assembly file contains information about itself. This information is called as Assembly Manifest.

Following steps are involved in creating shared assemblies :


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* Create your DLL/EXE source code * Generate unique assembly name using SN utility * Sign your DLL/EXE with the private key by modifying AssemblyInfo file * Compile your DLL/EXE * Place the resultant DLL/EXE in global assembly cache using AL utility

Q 155. What is global assembly cache?

Ans :- Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer. There are several ways to deploy an assembly into the global assembly cache: · Use an installer designed to work with the global assembly cache. This is the preferred option for installing assemblies into the global assembly cache. · Use a developer tool called the Global Assembly Cache tool (Gacutil.exe), provided by the .NET Framework SDK. · Use Windows Explorer to drag assemblies into the cache.

Q 156. What is MSIL?.

Ans :- When compiling to managed code, the compiler translates your source code into Microsoft intermediate language (MSIL), which is a CPU-independent set of instructions that can be efficiently converted to native code. MSIL includes instructions for loading, storing, initializing, and calling methods on objects, as well as instructions for arithmetic and logical operations, control flow, direct memory access, exception handling, and other operations. Before code can be run, MSIL must be converted to CPU-specific code, usually by a just-in-time (JIT) compiler. Because the common language runtime supplies one or more JIT compilers for each computer architecture it supports, the same set of MSIL can be JIT-compiled and run on any supported architecture. When a compiler produces MSIL, it also produces metadata. Metadata describes the types in your code, including the definition of each type, the signatures of each type's members, the members that your code references, and other data that the runtime uses at execution time. The MSIL and metadata are contained in a portable executable (PE) file that is based on and extends the published Microsoft PE and common object file format (COFF) used historically for executable content. This file format, which accommodates MSIL or native code as well as metadata, enables the


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operating system to recognize common language runtime images. The presence of metadata in the file along with the MSIL enables your code to describe itself, which means that there is no need for type libraries or Interface Definition Language (IDL). The runtime locates and extracts the metadata from the file as needed during execution.

Q 157. What is Jit compilers?.how many are available in clr?

Ans :- Just-In-Time compiler- it converts the language that you write in .Net into machine language that a computer can understand. there are tqo types of JITs one is memory optimized & other is performace optimized.

Q 158. What is tracing?Where it used.Explain few methods available

Ans :- Tracing refers to collecting information about the application while it is running. You use tracing information to troubleshoot an application. Tracing allows us to observe and correct programming errors. Tracing enables you to record information in various log files about the errors that might occur at run time. You can analyze these log files to find the cause of the errors.

In .NET we have objects called Trace Listeners. A listener is an object that receives the trace output and outputs it somewhere; that somewhere could be a window in your development environment, a file on your hard drive, a Windows Event log, a SQL Server or Oracle database, or any other customized data store.

The System.Diagnostics namespace provides the interfaces, classes, enumerations and structures that are used for tracing The System.Diagnostics namespace provides two classes named Trace and Debug that are used for writing errors and application execution information in logs.

All Trace Listeners have the following functions. Functionality of these functions is same except that the target media for the tracing output is determined by the Trace Listener.

Method Name Result Fail Outputs the specified text with the Call Stack. Write Outputs the specified text. WriteLine Outputs the specified text and a carriage return. Flush Flushes the output buffer to the target media.


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Close Closes the output stream in order to not receive the tracing/debugging output.

Q 159. How to set the debug mode?

Ans :- Debug Mode for ASP.NET applications - To set ASP.NET appplication in debugging mode, edit the application's web.config and assign the "debug" attribute in < compilation > section to "true" as show below: < configuration > < system.web > < compilation defaultLanguage="vb" debug="true" / > .... ... .. < / configuration >

This case-sensitive attribute 'debug tells ASP.NET to generate symbols for dynamically generated files and enables the debugger to attach to the ASP.NET application. ASP.NET will detect this change automatically, without the need to restart the server. Debug Mode for ASP.NET Webservices - Debugging an XML Web service created with ASP.NET is similar to the debugging an ASP.NET Web application.

Q 160. What is the property available to check if the page posted or not?

Ans :- The Page_Load event handler in the page checks for IsPostBack property value, to ascertain whether the page is posted. The Page.IsPostBack gets a value indicating whether the page is being loaded in response to the client postback, or it is for the first time. The value of Page.IsPostBack is True, if the page is being loaded in response to the client postback; while its value is False, when the page is loaded for the first time. The Page.IsPostBack property facilitates execution of certain routine in Page_Load, only once (for e.g. in Page load, we need to set default value in controls, when page is loaded for the first time. On post back, we check for true value for IsPostback value and then invoke server-side code to update data).

Q 161. Which are the abstract classes available under system.xml namespace?

Ans :- The System.XML namespace provides XML related processing ability in .NET


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framework. XmlReader and XMLWriter are the two abstract classes at the core of .NET Framework XML classes:

1. XmlReader provides a fast, forward-only, read-only cursor for processing an XML document stream. 2. XmlWriter provides an interface for producing XML document streams that conform to the W3C's XML standards.

Both XmlReader and XmlWriter are abstract base classes, which define the functionality that all derived classes must support.

Q 162. Is it possible to use multipe inheritance in .net?

Ans :- Multiple Inheritance is an ability to inherit from more than one base class i.e. ability of a class to have more than one superclass, by inheriting from different sources and thus combine separately-defined behaviors in a single class. There are two types of multiple inheritance: multiple type/interface inheritance and multiple implementation inheritance. C# & VB.NET supports only multiple type/interface inheritance, i.e. you can derive an class/interface from multiple interfaces. There is no support for multiple implementation inheritance in .NET. That means a class can only derived from one class.

Q 163. What are the derived classes from xmlReader and xmlWriter?

Ans :- Both XmlReader and XmlWriter are abstract base classes, which define the functionality that all derived classes must support. There are three concrete implementations of XmlReader: 1.XmlTextReader 2.XmlNodeReader 3.XmlValidatingReader There are two concrete implementations of XmlWriter: 1.XmlTextWriter 2.XmlNodeWriter XmlTextReader and XmlTextWriter support reading data to/from text-based stream, while XmlNodeReader and XmlNodeWriter are designed for working with in-memory DOM tree structure. The custom readers and writers can also be developed to extend the built-in functionality of XmlReader and XmlWriter.

Q 164. What is managed and unmanaged code?


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Ans :- The .NET framework provides several core run-time services to the programs that run within it - for example exception handling and security. For these services to work, the code must provide a minimum level of information to the runtime. i.e., code executing under the control of the CLR is called managed code. For example, any code written in C# or Visual Basic .NET is managed code.

Code that runs outside the CLR is referred to as "unmanaged code." COM components, ActiveX components, and Win32 API functions are examples of unmanaged code.

Q 165. How you deploy .NET assemblies?

Ans :- One way is simply use xcopy. others are use and the setup projects in .net. and one more way is use of nontuch deployment.

Q 166. What is Globalizationa and Localization ? Ans :- Globalization is the process of creating an application that meets the needs of users from multiple cultures. It includes using the correct currency, date and time format, calendar, writing direction, sorting rules, and other issues. Accommodating these cultural differences in an application is called localization.Using classes of System.Globalization namespace, you can set application's current culture.

This can be achieved by using any of the following 3 approaches. 1. Detect and redirect 2. Run-time adjustment 3. Using Satellite assemblies. Q 167. Whate are Resource Files ? How are they used in .NET?

Ans :- Resource files are the files containing data that is logically deployed with an application.These files can contain data in a number of formats including strings, images and persisted objects. It has the main advantage of If we store data in these files then we don't need to compile these if the data get changed. In .NET we basically require them storing culture specific informations by localizing application's resources. You can deploy your resources using satellite assemblies.

Q 168. Difference between Dispose and Finallize method?


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Ans :- Finalize method is used to free the memory used by some unmanaged resources like window handles (HWND). It's similar to the destructor syntax in C#. The GC calls this method when it founds no more references to the object. But, In some cases we may need release the memory used by the resources explicitely.To release the memory explicitly we need to implement the Dispose method of IDisposable interface.

Q 169. What is encapsulation ?

Ans :- Encapsulation is the ability to hide the internal workings of an object's behavior and its data. For instance, let's say you have a object named Bike and this object has a method named start(). When you create an instance of a Bike object and call its start() method you are not worried about what happens to accomplish this, you just want to make sure the state of the bike is changed to 'running' afterwards. This kind of behavior hiding is encapsulation and it makes programming much easier.

Q 170. How can you prevent your class to be inherated further?

Ans:- By setting Sealed - Key word

public sealed class Planet { //code goes here }

class Moon:Planet { //Not allowed as base class is sealed }

Q 171. What is GUID and why we need to use it and in what condition? How this is Created?

Ans :- A GUID is a 128-bit integer (16 bytes) that can be used across all computers and networks wherever a unique identifier is required. Such an identifier has a very


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low probability of being duplicated. Visual Studio .NET IDE has a utility under the tools menu to generate GUIDs.

Q 172. Why do you need to serialize.?

Ans :- We need to serialize the object,if you want to pass object from one computer/application domain to another.Process of converting complex objects into stream of bytes that can be persisted or transported.Namespace for serialization is System.Runtime.Serialization.The ISerializable interface allows you to make any class Serializable..NET framework features 2 serializing method. 1.Binary Serialization 2.XML Serialization

Q 173. What is inline schema, how does it works?

Ans :- Schemas can be included inside of XML file is called Inline Schemas.This is useful when it is inconvenient to physically seprate the schema and the XML document.A schema is an XML document that defines the structure, constraints, data types, and relationships of the elements that constitute the data contained inside the XML document or in another XML document.Schema can be an external file which uses the XSD or XDR extension called external schema. Inline schema can take place even when validation is turned off.

Q 174. Describe the advantages of writing a managed code application instead of unmanaged one. What's involved in certain piece of code being managed?

Ans :- "Advantage includes automatic garbage collection,memory management,security,type checking,versioning

Managed code is compiled for the .NET run-time environment. It runs in the Common Language Runtime (CLR), which is the heart of the .NET Framework. The CLR provides services such as security, memory management, and cross-language integration. Managed applications written to take advantage of the features of the CLR perform more efficiently and safely, and take better advantage of developers existing expertise in languages that support the .NET Framework.


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Unmanaged code includes all code written before the .NET Framework was introduced�this includes code written to use COM, native Win32, and Visual Basic 6. Because it does not run inside the .NET environment, unmanaged code cannot make use of any .NET managed facilities."

Q 175. What are multicast delegates ? give me an example ?

Ans :- Delegate that can have more than one element in its invocation List.

using System; namespace SampleMultiCastDelegate { class MultiCast { public delegate string strMultiCast(string s); } }

MainClass defines the static methods having same signature as delegate. using System;

namespace SampleMultiCastDelegate { public class MainClass { public MainClass() { }

public static string Jump(string s) { Console.WriteLine("Jump"); return String.Empty; }

public static string Run(string s) { Console.WriteLine("Run");


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return String.Empty; }

public static string Walk(string s) { Console.WriteLine("Walk"); return String.Empty; } } }

The Main class:

using System; using System.Threading; namespace SampleMultiCastDelegate { public class MainMultiCastDelegate { public static void Main() { MultiCast.strMultiCast Run,Walk,Jump;

MultiCast.strMultiCast myDelegate;

///here mydelegate used the Combine method of System.MulticastDelegate ///and the delegates combine myDelegate=(MultiCast.strMultiCast)System.Delegate.Combine(Run,Walk); } } }

Q 176. Can a nested object be used in Serialization ?

Ans :- Yes. If a class that is to be serialized contains references to objects of other classes, and if those classes have been marked as serializable, then their objects are serialized too.


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Q 177. Difference between int and int32 ?

Ans :- Both are same. System.Int32 is a .NET class. Int is an alias name for System.Int32.

Q 178. Describe the difference between a Thread and a Process?

Ans :- A Process is an instance of an running application. And a thread is the Execution stream of the Process. A process can have multiple Thread. When a process starts a specific memory area is allocated to it. When there is multiple thread in a process, each thread gets a memory for storing the variables in it and plus they can access to the global variables which is common for all the thread. Eg.A Microsoft Word is a Application. When you open a word file,an instance of the Word starts and a process is allocated to this instance which has one thread.

Q 179.What is the difference between an EXE and a DLL?

Ans :- You can create an objects of Dll but not of the EXE. Dll is an In-Process Component whereas EXE is an OUt-Process Component. Exe is for single use whereas you can use Dll for multiple use. Exe can be started as standalone where dll cannot be.

Q 180. What is strong-typing versus weak-typing? Which is preferred? Why?

Ans :- Strong typing implies that the types of variables involved in operations are associated to the variable, checked at compile-time, and require explicit conversion; weak typing implies that they are associated to the value, checked at run-time, and are implicitly converted as required. (Which is preferred is a disputable point, but I personally prefer strong typing because I like my errors to be found as soon as possible.)

Q 190. What is a PID? How is it useful when troubleshooting a system?

Ans :- PID is the process Id of the application in Windows. Whenever a process


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starts running in the Windows environment, it is associated with an individual process Id or PID.

The PID (Process ID) a unique number for each item on the Process Tab, Image Name list. How do you get the PID to appear? In Task Manger, select the View menu, then select columns and check PID (Process Identifier).

In Linux, PID is used to debug a process explicitly. However we cannot do this in a windows environment.

Microsoft has launched a SDK called as Microsoft Operations Management (MOM). This uses the PID to find out which dll�s have been loaded by a process in the memory. This is essentially helpful in situations where the Process which has a memory leak is to be traced to a erring dll. Personally I have never used a PID, our Windows debugger does the things required to find out.

Q 191. What is the GAC? What problem does it solve?

Ans :- Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies that are to be shared by several applications on the computer. This area is typically the folder under windows or winnt in the machine.

All the assemblies that need to be shared across applications need to be done through the Global assembly Cache only. However it is not necessary to install assemblies into the global assembly cache to make them accessible to COM interop or unmanaged code.

There are several ways to deploy an assembly into the global assembly cache: · Use an installer designed to work with the global assembly cache. This is the preferred option for installing assemblies into the global assembly cache. · Use a developer tool called the Global Assembly Cache tool (Gacutil.exe), provided by the .NET Framework SDK. · Use Windows Explorer to drag assemblies into the cache.

GAC solves the problem of DLL Hell and DLL versioning. Unlike earlier situations, GAC can hold two assemblies of the same name but different version. This ensures that the applications which access a particular assembly continue to access the same assembly even if another version of that assembly is installed on that machine.


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Q 192. Describe what an Interface is and how it�s different from a Class.

Ans :- An interface is a structure of code which is similar to a class. An interface is a prototype for a class and is useful from a logical design perspective. Interfaces provide a means to define the protocols for a class without worrying about the implementation details. The syntax for creating interfaces follows: interface Identifier { InterfaceBody }

Identifier is the name of the interface and InterfaceBody refers to the abstract methods and static final variables that make up the interface. Because it is assumed that all the methods in an interface are abstract, it isn't necessary to use the abstract keyword

An interface is a description of some of the members available from a class. In practice, the syntax typically looks similar to a class definition, except that there's no code defined for the methods � just their name, the arguments passed and the type of the value returned. So what good is it? None by itself. But you create an interface so that classes will implement it.

But what does it mean to implement an interface. The interface acts as a contract or promise. If a class implements an interface, then it must have the properties and methods of the interface defined in the class. This is enforced by the compiler.

Broadly the differentiators between classes and interfaces is as follows � Interface should not have any implementation. � Interface can not create any instance. � Interface should provide high level abstraction from the implementation. � Interface can have multiple inheritances. � Default access level of the interface is public.

Q 193. What is the difference between XML Web Services using ASMX and .NET Remoting using SOAP?

Ans :- ASP.NET Web services and .NET Remoting provide a full suite of design options for cross-process and cross-plaform communication in distributed applications. In general, ASP.NET Web services provide the highest levels of interoperability with full support for WSDL and SOAP over HTTP, while .NET


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Remoting is designed for common language runtime type-system fidelity and supports additional data format and communication channels. Hence if we looking cross-platform communication than web services is the choice coz for .NET remoting .Net framework is requried which may or may not present for the other platform.

Serialization and Metadata ASP.NET Web services rely on the System.Xml.Serialization.XmlSerializer class to marshal data to and from SOAP messages at runtime. For metadata, they generate WSDL and XSD definitions that describe what their messages contain. The reliance on pure WSDL and XSD makes ASP.NET Web services metadata portable; it expresses data structures in a way that other Web service toolkits on different platforms and with different programming models can understand. In some cases, this imposes constraints on the types you can expose from a Web service�XmlSerializer will only marshal things that can be expressed in XSD. Specifically, XmlSerializer will not marshal object graphs and it has limited support for container types.

.NET Remoting relies on the pluggable implementations of the IFormatter interface used by the System.Runtime.Serialization engine to marshal data to and from messages. There are two standard formatters, System.Runtime.Serialization.Formatters.Binary.BinaryFormatter and System.Runtime.Serialization.Formatters.Soap.SoapFormatter. The BinaryFormatter and SoapFormatter, as the names suggest, marshal types in binary and SOAP format respectively. For metadata, .NET Remoting relies on the common language runtime assemblies, which contain all the relevant information about the data types they implement, and expose it via reflection. The reliance on the assemblies for metadata makes it easy to preserve the full runtime type-system fidelity. As a result, when the .NET Remoting plumbing marshals data, it includes all of a class's public and private members; handles object graphs correctly; and supports all container types (e.g., System.Collections.Hashtable). However, the reliance on runtime metadata also limits the reach of a .NET Remoting system�a client has to understand .NET constructs in order to communicate with a .NET Remoting endpoint. In addition to pluggable formatters, the .NET Remoting layer supports pluggable channels, which abstract away the details of how messages are sent. There are two standard channels, one for raw TCP and one for HTTP. Messages can be sent over either channel independent of format.

Distributed Application Design: ASP.NET Web Services vs. .NET Remoting ASP.NET Web services favor the XML Schema type system, and provide a simple programming model with broad cross-platform reach. .NET Remoting favors the runtime type system, and provides a more complex programming model with much


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more limited reach. This essential difference is the primary factor in determining which technology to use. However, there are a wide range of other design factors, including transport protocols, host processes, security, performance, state management, and support for transactions to consider as well.

Security Since ASP.NET Web services rely on HTTP, they integrate with the standard Internet security infrastructure. ASP.NET leverages the security features available with IIS to provide strong support for standard HTTP authentication schemes including Basic, Digest, digital certificates, and even Microsoft® .NET Passport. (You can also use Windows Integrated authentication, but only for clients in a trusted domain.) One advantage of using the available HTTP authentication schemes is that no code change is required in a Web service; IIS performs authentication before the ASP.NET Web services are called. ASP.NET also provides support for .NET Passport-based authentication and other custom authentication schemes. ASP.NET supports access control based on target URLs, and by integrating with the .NET code access security (CAS) infrastructure. SSL can be used to ensure private communication over the wire.

Although these standard transport-level techniques to secure Web services are quite effective, they only go so far. In complex scenarios involving multiple Web services in different trust domains, you have to build custom ad hoc solutions. Microsoft and others are working on a set of security specifications that build on the extensibility of SOAP messages to offer message-level security capabilities. One of these is the XML Web Services Security Language (WS-Security), which defines a framework for message-level credential transfer, message integrity, and message confidentiality.

As noted in the previous section, the .NET Remoting plumbing does not secure cross-process invocations in the general case. A .NET Remoting endpoint hosted in IIS with ASP.NET can leverage all the same security features available to ASP.NET Web services, including support for secure communication over the wire using SSL. If you are using the TCP channel or the HTTP channel hosted in processes other than aspnet_wp.exe, you have to implement authentication, authorization and privacy mechanisms yourself.

One additional security concern is the ability to execute code from a semi-trusted environment without having to change the default security policy. ASP.NET Web Services client proxies work in these environments, but .NET Remoting proxies do not. In order to use a .NET Remoting proxy from a semi-trusted environment, you need a special serialization permission that is not given to code loaded from your intranet or the Internet by default. If you want to use a .NET Remoting client from


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within a semi-trusted environment, you have to alter the default security policy for code loaded from those zones. In situations where you are connecting to systems from clients running in a sandbox�like a downloaded Windows Forms application, for instance�ASP.NET Web Services are a simpler choice because security policy changes are not required.

Conceptually, what is the difference between early-binding and late-binding? Early binding � Binding at Compile Time Late Binding � Binding at Run Time

Early binding implies that the class of the called object is known at compile-time; late-binding implies that the class is not known until run-time, such as a call through an interface or via Reflection.

Early binding is the preferred method. It is the best performer because your application binds directly to the address of the function being called and there is no extra overhead in doing a run-time lookup. In terms of overall execution speed, it is at least twice as fast as late binding.

Early binding also provides type safety. When you have a reference set to the component's type library, Visual Basic provides IntelliSense support to help you code each function correctly. Visual Basic also warns you if the data type of a parameter or return value is incorrect, saving a lot of time when writing and debugging code.

Late binding is still useful in situations where the exact interface of an object is not known at design-time. If your application seeks to talk with multiple unknown servers or needs to invoke functions by name (using the Visual Basic 6.0 CallByName function for example) then you need to use late binding. Late binding is also useful to work around compatibility problems between multiple versions of a component that has improperly modified or adapted its interface between versions.

Q 194. What is an Asssembly Qualified Name? Is it a filename? How is it different?

Ans :- An assembly qualified name isn't the filename of the assembly; it's the internal name of the assembly combined with the assembly version, culture, and public key, thus making it unique.

e.g. (""System.Xml.XmlDocument, System.Xml, Version=1.0.3300.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"")


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Q 195. How is a strongly-named assembly different from one that isn�t strongly-named?

Ans :- Strong names are used to enable the stricter naming requirements associated with shared assemblies. These strong names are created by a .NET utility � sn.exe

Strong names have three goals: · Name uniqueness. Shared assemblies must have names that are globally unique. · Prevent name spoofing. Developers don't want someone else releasing a subsequent version of one of your assemblies and falsely claim it came from you, either by accident or intentionally. · Provide identity on reference. When resolving a reference to an assembly, strong names are used to guarantee the assembly that is loaded came from the expected publisher.

Strong names are implemented using standard public key cryptography. In general, the process works as follows: The author of an assembly generates a key pair (or uses an existing one), signs the file containing the manifest with the private key, and makes the public key available to callers. When references are made to the assembly, the caller records the public key corresponding to the private key used to generate the strong name.

Weak named assemblies are not suitable to be added in GAC and shared. It is essential for an assembly to be strong named.

Strong naming prevents tampering and enables assemblies to be placed in the GAC alongside other assemblies of the same name.

Q 196. How does the generational garbage collector in the .NET CLR manage object lifetime? What is non-deterministic finalization?

Ans :- The hugely simplistic version is that every time it garbage-collects, it starts by assuming everything to be garbage, then goes through and builds a list of everything reachable. Those become not-garbage, everything else doesn't, and gets thrown away. What makes it generational is that every time an object goes through this process and survives, it is noted as being a member of an older generation (up to 2, right now). When the garbage-collector is trying to free memory, it starts with the lowest generation (0) and only works up to higher ones if it can't free up enough space, on the grounds that shorter-lived objects are more likely to have been freed than longer-lived ones.


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Non-deterministic finalization implies that the destructor (if any) of an object will not necessarily be run (nor its memory cleaned up, but that's a relatively minor issue) immediately upon its going out of scope. Instead, it will wait until first the garbage collector gets around to finding it, and then the finalisation queue empties down to it; and if the process ends before this happens, it may not be finalised at all. (Although the operating system will usually clean up any process-external resources left open - note the usually there, especially as the exceptions tend to hurt a lot.)

Q 197. What is the difference between Finalize() and Dispose()?

Ans :- Dispose() is called by the user of an object to indicate that he is finished with it, enabling that object to release any unmanaged resources it holds. Finalize() is called by the run-time to allow an object which has not had Dispose() called on it to do the same. However, Dispose() operates determinalistically, whereas there is no guarantee that Finalize() will be called immediately when an object goes out of scope - or indeed at all, if the program ends before that object is GCed - and as such Dispose() is generally preferred.

Q 198. How is the using() pattern useful? What is IDisposable? How does it support deterministic finalization?

Ans :- The using() pattern is useful because it ensures that Dispose() will always be called when a disposable object (defined as one that implements IDisposable, and thus the Dispose() method) goes out of scope, even if it does so by an exception being thrown, and thus that resources are always released.

Q 199. What does this useful command line do? tasklist /m "mscor*"

Ans :- Lists all the applications and associated tasks/process currently running on the system with a module whose name begins "mscor" loaded into them; which in nearly all cases means "all the .NET processes".

Q 200. What�s wrong with a line like this? DateTime.Parse(myString);

Ans :- Therez nothing wrong with this declaration.Converts the specified string representation of a date and time to its DateTime equivalent.But If the string is not a valid DateTime,It throws an exception.


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Q 201. What are PDBs? Where must they be located for debugging to work?

Ans :- A program database (PDB) files holds debugging and project state information that allows incremental linking of debug configuration of your program.There are several different types of symbolic debugging information. The default type for Microsoft compiler is the so-called PDB file. The compiler setting for creating this file is /Zi, or /ZI for C/C++(which creates a PDB file with additional information that enables a feature called ""Edit and Continue"") or a Visual Basic/C#/JScript .NET program with /debug.

A PDB file is a separate file, placed by default in the Debug project subdirectory, that has the same name as the executable file with the extension .pdb. Note that the Visual C++ compiler by default creates an additional PDB file called VC60.pdb for VisulaC++6.0 and VC70.PDB file for VisulaC++7.0. The compiler creates this file during compilation of the source code, when the compiler isn't aware of the final name of the executable. The linker can merge this temporary PDB file into the main one if you tell it to, but it won't do it by default. The PDB file can be useful to display the detailed stack trace with source files and line numbers.

Q 202. What is FullTrust? Do GAC�ed assemblies have FullTrust?

Ans :- Before the .NET Framework existed, Windows had two levels of trust for downloaded code. This old model was a binary trust model. You only had two choices: Full Trust, and No Trust. The code could either do anything you could do, or it wouldn't run at all. The permission sets in .NET include FullTrust, SkipVerification, Execution, Nothing, LocalIntranet, Internet and Everything. Full Trust Grants unrestricted permissions to system resources. Fully trusted code run by a normal, nonprivileged user cannot do administrative tasks, but can access any resources the user can access, and do anything the user can do. From a security standpoint, you can think of fully trusted code as being similar to native, unmanaged code, like a traditional ActiveX control. GAC assemblies are granted FullTrust. In v1.0 and 1.1, the fact that assemblies in the GAC seem to always get a FullTrust grant is actually a side effect of the fact that the GAC lives on the local machine. If anyone were to lock down the security policy by changing the grant set of the local machine to something less than FullTrust, and if your assembly did not get extra permission from some other code group, it would no longer have FullTrust even though it lives in the GAC.


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Q 203. What does this do? gacutil /l | find /i "Corillian"

Ans :- Global Assembly Cache tool allows you to view and manipulate the contents of the global assembly cache and download cache.The tool comes with various optional params to do that. ""/l"" option Lists the contents of the global assembly cache. If you specify the assemblyName parameter(/l [assemblyName]), the tool lists only the assemblies matching that name.

Q 204. What does this do .. sn -t foo.dll ?

Ans :- Sn -t option displays the token for the public key stored in infile. The contents of infile must be previously generated using -p. Sn.exe computes the token using a hash function from the public key. To save space, the common language runtime stores public key tokens in the manifest as part of a reference to another assembly when it records a dependency to an assembly that has a strong name. The -tp option displays the public key in addition to the token.

Q 205. How do you generate a strong name?

Ans :- .NET provides an utility called strong name tool. You can run this toolfrom the VS.NET command prompt to generate a strong name with an option "-k" and providing the strong key file name. i.e. sn- -k < file-name >

What is the difference between a Debug and Release build? Is there a significant speed difference? Why or why not? The Debug build is the program compiled with full symbolic debug information and no optimization. The Release build is the program compiled employing optimization and contains no symbolic debug information. These settings can be changed as per need from Project Configuration properties. The release runs faster since it does not have any debug symbols and is optimized.

Q 206. Explain the use of virtual, sealed, override, and abstract.

Ans:- Abstract: The keyword can be applied for a class or method. 1. Class: If we use abstract keyword for a class it makes the class an abstract class, which means it cant be instantiated. Though it is not nessacary to make all the method within the abstract class to be virtual. ie,


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Abstract class can have concrete methods 2. Method: If we make a method as abstract, we dont need to provide implementation of the method in the class but the derived class need to implement/override this method. Sealed: It can be applied on a class and methods. It stops the type from further derivation i.e no one can derive class from a sealed class,ie A sealed class cannot be inherited.A sealed class cannot be a abstract class.A compile time error is thrown if you try to specify sealed class as a base class. When an instance method declaration includes a sealed modifier, that method is said to be a sealed method. If an instance method declaration includes the sealed modifier, it must also include the override modifier. Use of the sealed modifier prevents a derived class from further overriding the method For Egs: sealed override public void Sample() { Console.WriteLine("Sealed Method"); }

Virtual & Override: Virtual & Override keywords provides runtime polymorphism. A base class can make some of its methods as virtual which allows the derived class a chance to override the base class implementation by using override keyword. For e.g. class Shape { int a public virtual void Display() { Console.WriteLine("Shape"); } } class Rectangle:Shape { public override void Display() { Console.WriteLine("Derived"); } }


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Q 207.Explain the importance and use of each, Version, Culture and PublicKeyToken for an assembly.?

Ans :- This three alongwith name of the assembly provide a strong name or fully qualified name to the assembly. When a assebly is referenced with all three.

PublicKeyToken: Each assembly can have a public key embedded in its manifest that identifies the developer. This ensures that once the assembly ships, no one can modify the code or other resources contained in the assembly. Culture: Specifies which culture the assembly supports Version: The version number of the assembly.It is of the following form major.minor.build.revision.

Explain the differences between public, protected, private and internal. These all are access modifier and they governs the access level. They can be applied to class, methods, fields. Public: Allows class, methods, fields to be accessible from anywhere i.e. within and outside an assembly. Private: When applied to field and method allows to be accessible within a class. Protected: Similar to private but can be accessed by members of derived class also. Internal: They are public within the assembly i.e. they can be accessed by anyone within an assembly but outside assembly they are not visible.

Q 208. What is the difference between typeof(foo) and myFoo.GetType()?

Ans :- Typeof is operator which applied to a object returns System.Type object. Typeof cannot be overloaded white GetType has lot of overloads.GetType is a method which also returns System.Type of an object. GetType is used to get the runtime type of the object.

Example from MSDN showing Gettype used to retrive type at untime:-

public class MyBaseClass: Object { }

public class MyDerivedClass: MyBaseClass { }


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public class Test {

public static void Main() { MyBaseClass myBase = new MyBaseClass(); MyDerivedClass myDerived = new MyDerivedClass(); object o = myDerived; MyBaseClass b = myDerived;

Console.WriteLine("mybase: Type is {0}", myBase.GetType()); Console.WriteLine("myDerived: Type is {0}", myDerived.GetType()); Console.WriteLine("object o = myDerived: Type is {0}", o.GetType()); Console.WriteLine("MyBaseClass b = myDerived: Type is {0}", b.GetType()); } }

/*

This code produces the following output.

mybase: Type is MyBaseClass myDerived: Type is MyDerivedClass object o = myDerived: Type is MyDerivedClass MyBaseClass b = myDerived: Type is MyDerivedClass

*/

Q 209. Can "this" be used within a static method?

Ans :- No 'This' cannot be used in a static method. As only static variables/methods can be used in a static method.

Q 210. What is the purpose of XML Namespaces?

Ans ;- An XML Namespace is a collection of element types and attribute names. It consists of 2 parts 1) The first part is the URI used to identify the namespace 2) The second part is the element type or attribute name itself. Together they form a unique name. The various purpose of XML Namespace are


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1. Combine fragments from different documents without any naming conflicts. (See example below.) 2. Write reusable code modules that can be invoked for specific elements and attributes. Universally unique names guarantee that such modules are invoked only for the correct elements and attributes. 3. Define elements and attributes that can be reused in other schemas or instance documents without fear of name collisions. For example, you might use XHTML elements in a parts catalog to provide part descriptions. Or you might use the nil attribute defined in XML Schemas to indicate a missing value.

< Department > < Name >DVS1< /Name > < addr:Address xmlns:addr="http://www.tu-darmstadt.de/ito/addresses" > < addr:Street >Wilhelminenstr. 7< /addr:Street > < addr:City >Darmstadt< /addr:City > < addr:State >Hessen< /addr:State > < addr:Country >Germany< /addr:Country > < addr:PostalCode >D-64285< /addr:PostalCode > < /addr:Address > < serv:Server xmlns:serv="http://www.tu-darmstadt.de/ito/servers" > < serv:Name >OurWebServer< /serv:Name > < serv:Address >123.45.67.8< /serv:Address > < /serv:Server > < /Department >

Q 211. What is difference between MetaData and Manifest ?

Ans :- Metadata and Manifest forms an integral part of an assembly( dll / exe ) in .net framework . Out of which Metadata is a mandatory component , which as the name suggests gives the details about various components of IL code viz : Methods , properties , fields , class etc.

Essentially Metadata maintains details in form of tables like Methods Metadata tables , Properties Metadata tables , which maintains the list of given type and other details like access specifier , return type etc.

Now Manifest is a part of metadata only , fully called as �manifest metadata tables� , it contains the details of the references needed by the assembly of any other


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external assembly / type , it could be a custom assembly or standard System namespace .

Now for an assembly that can independently exists and used in the .Net world both the things ( Metadata with Manifest ) are mandatory , so that it can be fully described assembly and can be ported anywhere without any system dependency . Essentially .Net framework can read all assembly related information from assembly itself at runtime .

But for .Net modules , that can�t be used independently , until they are being packaged as a part of an assembly , they don�t contain Manifest but their complete structure is defined by their respective metadata .

Ultimately . .Net modules use Manifest Metadata tables of parent assembly which contain them .

Q 212. What is the use of Internal keyword?

Ans :- Internal keyword is one of the access specifier available in .Net framework , that makes a type visible in a given assembly , for e.g : a single dll can contain multiple modules , essentially a multi file assembly , but it forms a single binary component , so any type with internal keyword will be visible throughout the assembly and can be used in any of the modules .

Q 213. What actually happes when you add a something to arraylistcollection ?

Ans :- Following things will happen :

Arraylist is a dynamic array class in c# in System.Collections namespace derived from interfaces � ICollection , IList , ICloneable , IConvertible . It terms of in memory structure following is the implementation .

a. Check up the total space if there�s any free space on the declared list . b. If yes add the new item and increase count by 1 . c. If No Copy the whole thing to a temporary Array of Last Max. Size . d. Create new Array with size ( Last Array Size + Increase Value )


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e. Copy back values from temp and reference this new array as original array . f. Must doing Method updates too , need to check it up .

Q 214. What is Boxing and unboxing? Does it occure automaatically or u need to write code to box and unbox?

Ans :- Boxing � Process of converting a System.ValueType to Reference Type , Mostly base class System.Object type and allocating it memory on Heap .Reverse is unboxing , but can only be done with prior boxed variables.

Boxing is always implicit but Unboxing needs to be explicitly done via casting , thus ensuring the value type contained inside .

Q 215. How Boxing and unboxing occures in memory?

Ans :- Boxing converts value type to reference type , thus allocating memory on Heap . Unboxing converts already boxed reference types to value types through explicit casting , thus allocating memory on stack .

Q 216. Why only boxed types can be unboxed?

Ans :- Unboxing is the process of converting a Reference type variable to Value type and thus allocating memory on the stack . It happens only to those Reference type variables that have been earlier created by Boxing of a Value Type , therefore internally they contain a value type , which can be obtained through explicit casting . For any other Reference type , they don�t internally contain a Value type to Unboxed via explicit casting . This is why only boxed types can be unboxed .

Q 217. Explain what a diffgram is and its usage ?

Ans ;- A DiffGram is an XML format that is used to identify current and original versions of data elements. The DataSet uses the DiffGram format to load and persist its contents, and to serialize its contents for transport across a network connection. When a DataSet is written as a DiffGram, it populates the DiffGram with all the necessary information to accurately recreate the contents, though not the schema, of the DataSet, including column values from both the Original and Current row versions, row error information, and row order.


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When sending and retrieving a DataSet from an XML Web service, the DiffGram format is implicitly used. Additionally, when loading the contents of a DataSet from XML using the ReadXml method, or when writing the contents of a DataSet in XML using the WriteXml method, you can select that the contents be read or written as a DiffGram.

The DiffGram format is divided into three sections: the current data, the original (or "before") data, and an errors section, as shown in the following example.

<?xml version="1.0"?> <diffgr:diffgram xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<DataInstance> </DataInstance>

<diffgr:before> </diffgr:before>

<diffgr:errors> </diffgr:errors> </diffgr:diffgram>

The DiffGram format consists of the following blocks of data:

<DataInstance> The name of this element, DataInstance, is used for explanation purposes in this documentation. A DataInstance element represents a DataSet or a row of a DataTable. Instead of DataInstance, the element would contain the name of the DataSet or DataTable. This block of the DiffGram format contains the current data, whether it has been modified or not. An element, or row, that has been modified is identified with the diffgr:hasChanges annotation. <diffgr:before> This block of the DiffGram format contains the original version of a row. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation. <diffgr:errors> This block of the DiffGram format contains error information for a particular row in the DataInstance block. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation.


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Q 218. Can you edit data in the Repeater control?

Ans :- NO.

Q 219. Which are the different IsolationLevels ?

Ans :- Following are the various IsolationLevels:

• Serialized Data read by a current transaction cannot be changed by another transaction until the current transaction finishes. No new data can be inserted that would affect the current transaction. This is the safest isolation level and is the default.

• Repeatable Read Data read by a current transaction cannot be changed by another transaction until the current transaction finishes. Any type of new data can be inserted during a transaction.

• Read Committed A transaction cannot read data that is being modified by another transaction that has not committed. This is the default isolation level in Microsoft® SQL Server.

• Read Uncommitted A transaction can read any data, even if it is being modified by another transaction. This is the least safe isolation level but allows the highest concurrency.

• Any Any isolation level is supported. This setting is most commonly used by downstream components to avoid conflicts. This setting is useful because any downstream component must be configured with an isolation level that is equal to or less than the isolation level of its immediate upstream component. Therefore, a downstream component that has its isolation level configured as Any always uses the same isolation level that its immediate upstream component uses. If the root object in a transaction has its isolation level configured to Any, its isolation level becomes Serialized.

Q 220.How xml files and be read and write using dataset?.

Ans :- DataSet exposes method like ReadXml and WriteXml to read and write xml

Q 221. What are the different rowversions available?


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Ans :- There are four types of Rowversions. Current: The current values for the row. This row version does not exist for rows with a RowState of Deleted.

Default : The row the default version for the current DataRowState. For a DataRowState value of Added, Modified or Current, the default version is Current. For a DataRowState of Deleted, the version is Original. For a DataRowState value of Detached, the version is Proposed.

Original: The row contains its original values.

Proposed: The proposed values for the row. This row version exists during an edit operation on a row, or for a row that is not part of a DataRowCollection

Q 222. Explain acid properties?.

Ans :- The term ACID conveys the role transactions play in mission-critical applications. Coined by transaction processing pioneers, ACID stands for atomicity, consistency, isolation, and durability.

These properties ensure predictable behavior, reinforcing the role of transactions as all-or-none propositions designed to reduce the management load when there are many variables.

Atomicity A transaction is a unit of work in which a series of operations occur between the BEGIN TRANSACTION and END TRANSACTION statements of an application. A transaction executes exactly once and is atomic � all the work is done or none of it is.

Operations associated with a transaction usually share a common intent and are interdependent. By performing only a subset of these operations, the system could compromise the overall intent of the transaction. Atomicity eliminates the chance of processing a subset of operations.


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Consistency A transaction is a unit of integrity because it preserves the consistency of data, transforming one consistent state of data into another consistent state of data.

Consistency requires that data bound by a transaction be semantically preserved. Some of the responsibility for maintaining consistency falls to the application developer who must make sure that all known integrity constraints are enforced by the application. For example, in developing an application that transfers money, you should avoid arbitrarily moving decimal points during the transfer.

Isolation A transaction is a unit of isolation � allowing concurrent transactions to behave as though each were the only transaction running in the system.

Isolation requires that each transaction appear to be the only transaction manipulating the data store, even though other transactions may be running at the same time. A transaction should never see the intermediate stages of another transaction.

Transactions attain the highest level of isolation when they are serializable. At this level, the results obtained from a set of concurrent transactions are identical to the results obtained by running each transaction serially. Because a high degree of isolation can limit the number of concurrent transactions, some applications reduce the isolation level in exchange for better throughput.

Durability A transaction is also a unit of recovery. If a transaction succeeds, the system guarantees that its updates will persist, even if the computer crashes immediately after the commit. Specialized logging allows the system's restart procedure to complete unfinished operations, making the transaction durable.

Q 223. Whate are different types of Commands available with DataAdapter ?

Ans :- The SqlDataAdapter has SelectCommand, InsertCommand, DeleteCommand and UpdateCommand

Q 224. What is a Dataset?

Ans :- Datasets are the result of bringing together ADO and XML. A dataset


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contains one or more data of tabular XML, known as DataTables, these data can be treated separately, or can have relationships defined between them. Indeed these relationships give you ADO data SHAPING without needing to master the SHAPE language, which many people are not comfortable with.

The dataset is a disconnected in-memory cache database. The dataset object model looks like this:

Dataset DataTableCollection DataTable DataView DataRowCollection DataRow DataColumnCollection DataColumn ChildRelations ParentRelations Constraints PrimaryKey DataRelationCollection

Let�s take a look at each of these:

DataTableCollection: As we say that a DataSet is an in-memory database. So it has this collection, which holds data from multiple tables in a single DataSet object.

DataTable: In the DataTableCollection, we have DataTable objects, which represents the individual tables of the dataset.

DataView: The way we have views in database, same way we can have DataViews. We can use these DataViews to do Sort, filter data.

DataRowCollection: Similar to DataTableCollection, to represent each row in each Table we have DataRowCollection.

DataRow: To represent each and every row of the DataRowCollection, we have DataRows.

DataColumnCollection: Similar to DataTableCollection, to represent each column in each Table we have DataColumnCollection.


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DataColumn: To represent each and every Column of the DataColumnCollection, we have DataColumn.

PrimaryKey: Dataset defines Primary key for the table and the primary key validation will take place without going to the database.

Constraints: We can define various constraints on the Tables, and can use Dataset.Tables(0).enforceConstraints. This will execute all the constraints, whenever we enter data in DataTable.

DataRelationCollection: as we know that we can have more than 1 table in the dataset, we can also define relationship between these tables using this collection and maintain a parent-child relationship.

Q 225.Explain the ADO . Net Architecture ( .Net Data Provider)

Ans :- ADO.N et is the data access model for .Net �based applications. It can be used to access relational database systems such as SQL SERVER 2000, Oracle, and many other data sources for which there is an OLD DB or ODBC provider. To a certain extent, ADO.NET represents the latest evolution of ADO technology. However, ADO.NET introduces some major changes and innovations that are aimed at the loosely coupled and inherently disconnected � nature of web applications.

A .Net Framework data provider is used to connecting to a database, executing commands, and retrieving results. Those results are either processed directly, or placed in an ADO.NET DataSet in order to be exposed to the user in an ad-hoc manner, combined with data from multiple sources, or remoted between tiers. The .NET Framework data provider is designed to be lightweight, creating a minimal layer between the data source and your code, increasing performance without sacrificing functionality.

Following are the 4 core objects of .Net Framework Data provider:

• Connection: Establishes a connection to a specific data source

• Command: Executes a command against a data source. Exposes Parameters and can execute within the scope of a Transaction from a Connection.

• DataReader: Reads a forward-only, read-only stream of data from a data source.


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• DataAdapter: Populates a DataSet and resolves updates with the data source.

The .NET Framework includes the .NET Framework Data Provider for SQL Server (for Microsoft SQL Server version 7.0 or later), the .NET Framework Data Provider for OLE DB, and the .NET Framework Data Provider for ODBC.

The .NET Framework Data Provider for SQL Server: The .NET Framework Data Provider for SQL Server uses its own protocol to communicate with SQL Server. It is lightweight and performs well because it is optimized to access a SQL Server directly without adding an OLE DB or Open Database Connectivity (ODBC) layer. The following illustration contrasts the .NET Framework Data Provider for SQL Server with the .NET Framework Data Provider for OLE DB. The .NET Framework Data Provider for OLE DB communicates to an OLE DB data source through both the OLE DB Service component, which provides connection pooling and transaction services, and the OLE DB Provider for the data source

The .NET Framework Data Provider for OLE DB: The .NET Framework Data Provider for OLE DB uses native OLE DB through COM interoperability to enable data access. The .NET Framework Data Provider for OLE DB supports both local and distributed transactions. For distributed transactions, the .NET Framework Data Provider for OLE DB, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.

The .NET Framework Data Provider for ODBC: The .NET Framework Data Provider for ODBC uses native ODBC Driver Manager (DM) through COM interoperability to enable data access. The ODBC data provider supports both local and distributed transactions. For distributed transactions, the ODBC data provider, by default, automatically enlists in a transaction and obtains transaction details from Windows 2000 Component Services.

The .NET Framework Data Provider for Oracle: The .NET Framework Data Provider for Oracle enables data access to Oracle data sources through Oracle client connectivity software. The data provider supports Oracle client software version 8.1.7 and later. The data provider supports both local and distributed transactions (the data provider automatically enlists in existing distributed transactions, but does not currently support the EnlistDistributedTransaction method).

The .NET Framework Data Provider for Oracle requires that Oracle client software (version 8.1.7 or later) be installed on the system before you can use it to connect to an Oracle data source.


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.NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You will need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider. Choosing a .NET Framework Data Provider

.NET Framework Data Provider for SQL Server: Recommended for middle-tier applications using Microsoft SQL Server 7.0 or later. Recommended for single-tier applications using Microsoft Data Engine (MSDE) or Microsoft SQL Server 7.0 or later. Recommended over use of the OLE DB Provider for SQL Server (SQLOLEDB) with the .NET Framework Data Provider for OLE DB. For Microsoft SQL Server version 6.5 and earlier, you must use the OLE DB Provider for SQL Server with the .NET Framework Data Provider for OLE DB.

.NET Framework Data Provider for OLE DB: Recommended for middle-tier applications using Microsoft SQL Server 6.5 or earlier, or any OLE DB provider. For Microsoft SQL Server 7.0 or later, the .NET Framework Data Provider for SQL Server is recommended. Recommended for single-tier applications using Microsoft Access databases. Use of a Microsoft Access database for a middle-tier application is not recommended.

.NET Framework Data Provider for ODBC: Recommended for middle-tier applications using ODBC data sources. Recommended for single-tier applications using ODBC data sources.

.NET Framework Data Provider for Oracle: Recommended for middle-tier applications using Oracle data sources. Recommended for single-tier applications using Oracle data sources. Supports Oracle client software version 8.1.7 and later. The .NET Framework Data Provider for Oracle classes are located in the System.Data.OracleClient namespace and are contained in the System.Data.OracleClient.dll assembly. You need to reference both the System.Data.dll and the System.Data.OracleClient.dll when compiling an application that uses the data provider.

Can you explain the difference between an ADO.NET Dataset and an ADO Recordset? Let�s take a look at the differences between ADO Recordset and ADO.Net DataSet:


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1. Table Collection: ADO Recordset provides the ability to navigate through a single table of information. That table would have been formed with a join of multiple tables and returning columns from multiple tables. ADO.NET DataSet is capable of holding instances of multiple tables. It has got a Table Collection, which holds multiple tables in it. If the tables are having a relation, then it can be manipulated on a Parent-Child relationship. It has the ability to support multiple tables with keys, constraints and interconnected relationships. With this ability the DataSet can be considered as a small, in-memory relational database cache.

2. Navigation: Navigation in ADO Recordset is based on the cursor mode. Even though it is specified to be a client-side Recordset, still the navigation pointer will move from one location to another on cursor model only. ADO.NET DataSet is an entirely offline, in-memory, and cache of data. All of its data is available all the time. At any time, we can retrieve any row or column, constraints or relation simply by accessing it either ordinarily or by retrieving it from a name-based collection.

3. Connectivity Model: The ADO Recordset was originally designed without the ability to operate in a disconnected environment. ADO.NET DataSet is specifically designed to be a disconnected in-memory database. ADO.NET DataSet follows a pure disconnected connectivity model and this gives it much more scalability and versatility in the amount of things it can do and how easily it can do that.

4. Marshalling and Serialization: In COM, through Marshalling, we can pass data from 1 COM component to another component at any time. Marshalling involves copying and processing data so that a complex type can appear to the receiving component the same as it appeared to the sending component. Marshalling is an expensive operation. ADO.NET Dataset and DataTable components support Remoting in the form of XML serialization. Rather than doing expensive Marshalling, it uses XML and sent data across boundaries.

5. Firewalls and DCOM and Remoting: Those who have worked with DCOM know that how difficult it is to marshal a DCOM component across a router. People generally came up with workarounds to solve this issue. ADO.NET DataSet uses Remoting, through which a DataSet / DataTable component can be serialized into XML, sent across the wire to a new AppDomain, and then Desterilized back to a fully functional DataSet. As the DataSet is completely disconnected, and it has no dependency, we lose absolutely nothing by serializing and transferring it through Remoting.

Q 226. How do you handle data concurrency in .NET ?


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Ans :- One of the key features of the ADO.NET DataSet is that it can be a self-contained and disconnected data store. It can contain the schema and data from several rowsets in DataTable objects as well as information about how to relate the DataTable objects-all in memory. The DataSet neither knows nor cares where the data came from, nor does it need a link to an underlying data source. Because it is data source agnostic you can pass the DataSet around networks or even serialize it to XML and pass it across the Internet without losing any of its features. However, in a disconnected model, concurrency obviously becomes a much bigger problem than it is in a connected model.

In this column, I'll explore how ADO.NET is equipped to detect and handle concurrency violations. I'll begin by discussing scenarios in which concurrency violations can occur using the ADO.NET disconnected model. Then I will walk through an ASP.NET application that handles concurrency violations by giving the user the choice to overwrite the changes or to refresh the out-of-sync data and begin editing again. Because part of managing an optimistic concurrency model can involve keeping a timestamp (rowversion) or another type of flag that indicates when a row was last updated, I will show how to implement this type of flag and how to maintain its value after each database update.

Is Your Glass Half Full?

There are three common techniques for managing what happens when users try to modify the same data at the same time: pessimistic, optimistic, and last-in wins. They each handle concurrency issues differently.

The pessimistic approach says: "Nobody can cause a concurrency violation with my data if I do not let them get at the data while I have it." This tactic prevents concurrency in the first place but it limits scalability because it prevents all concurrent access. Pessimistic concurrency generally locks a row from the time it is retrieved until the time updates are flushed to the database. Since this requires a connection to remain open during the entire process, pessimistic concurrency cannot successfully be implemented in a disconnected model like the ADO.NET DataSet, which opens a connection only long enough to populate the DataSet then releases and closes, so a database lock cannot be held.

Another technique for dealing with concurrency is the last-in wins approach. This model is pretty straightforward and easy to implement-whatever data modification was made last is what gets written to the database. To implement this technique you only need to put the primary key fields of the row in the UPDATE statement's


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WHERE clause. No matter what is changed, the UPDATE statement will overwrite the changes with its own changes since all it is looking for is the row that matches the primary key values. Unlike the pessimistic model, the last-in wins approach allows users to read the data while it is being edited on screen. However, problems can occur when users try to modify the same data at the same time because users can overwrite each other's changes without being notified of the collision. The last-in wins approach does not detect or notify the user of violations because it does not care. However the optimistic technique does detect violations. Contd....

In optimistic concurrency models, a row is only locked during the update to the database. Therefore the data can be retrieved and updated by other users at any time other than during the actual row update operation. Optimistic concurrency allows the data to be read simultaneously by multiple users and blocks other users less often than its pessimistic counterpart, making it a good choice for ADO.NET. In optimistic models, it is important to implement some type of concurrency violation detection that will catch any additional attempt to modify records that have already been modified but not committed. You can write your code to handle the violation by always rejecting and canceling the change request or by overwriting the request based on some business rules. Another way to handle the concurrency violation is to let the user decide what to do. The sample application that is shown in Figure 1 illustrates some of the options that can be presented to the user in the event of a concurrency violation.

Where Did My Changes Go?

When users are likely to overwrite each other's changes, control mechanisms should be put in place. Otherwise, changes could be lost. If the technique you're using is the last-in wins approach, then these types of overwrites are entirely possible.For example, imagine Julie wants to edit an employee's last name to correct the spelling. She navigates to a screen which loads the employee's information into a DataSet and has it presented to her in a Web page. Meanwhile, Scott is notified that the same employee's phone extension has changed. While Julie is correcting the employee's last name, Scott begins to correct his extension. Julie saves her changes first and then Scott saves his.Assuming that the application uses the last-in wins approach and updates the row using a SQL WHERE clause containing only the primary key's value, and assuming a change to one column requires the entire row to be updated, neither Julie nor Scott may immediatelyrealize the concurrency issue that just occurred. In this particular situation, Julie's changes were overwritten by Scott's changes because he saved last, and the last name reverted to the misspelled version.


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So as you can see, even though the users changed different fields, their changes collided and caused Julie's changes to be lost. Without some sort of concurrency detection and handling, these types of overwrites can occur and even go unnoticed.When you run the sample application included in this column's download, you should open two separate instances of Microsoft® Internet Explorer. When I generated the conflict, I opened two instances to simulate two users with two separate sessions so that a concurrency violation would occur in the sample application. When you do this, be careful not to use Ctrl+N because if you open one instance and then use the Ctrl+N technique to open another instance, both windows will share the same session.

Detecting Violations

The concurrency violation reported to the user in Figure 1 demonstrates what can happen when multiple users edit the same data at the same time. In Figure 1, the user attempted to modify the first name to "Joe" but since someone else had already modified the last name to "Fuller III," a concurrency violation was detected and reported. ADO.NET detects a concurrency violation when a DataSet containing changed values is passed to a SqlDataAdapter's Update method and no rows are actually modified. Simply using the primary key (in this case the EmployeeID) in the UPDATE statement's WHERE clause will not cause a violation to be detected because it still updates the row (in fact, this technique has the same outcome as the last-in wins technique). Instead, more conditions must be specified in the WHERE clause in order for ADO.NET to detect the violation.

The key here is to make the WHERE clause explicit enough so that it not only checks the primary key but that it also checks for another appropriate condition. One way to accomplish this is to pass in all modifiable fields to the WHERE clause in addition to the primary key. For example, the application shown in Figure 1 could have its UPDATE statement look like the stored procedure that's shown in Figure 2.

Notice that in the code in Figure 2 nullable columns are also checked to see if the value passed in is NULL. This technique is not only messy but it can be difficult to maintain by hand and it requires you to test for a significant number of WHERE conditions just to update a row. This yields the desired result of only updating rows where none of the values have changed since the last time the user got the data, but there are other techniques that do not require such a huge WHERE clause.

Another way to make sure that the row is only updated if it has not been modified by another user since you got the data is to add a timestamp column to the table. The SQL Server(tm) TIMESTAMP datatype automatically updates itself with a new


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value every time a value in its row is modified. This makes it a very simple and convenient tool to help detect concurrency violations.

A third technique is to use a DATETIME column in which to track changes to its row. In my sample application I added a column called LastUpdateDateTime to the Employees table.

ALTER TABLE Employees ADD LastUpdateDateTime DATETIME

There I update the value of the LastUpdateDateTime field automatically in the UPDATE stored procedure using the built-in SQL Server GETDATE function.

The binary TIMESTAMP column is simple to create and use since it automatically regenerates its value each time its row is modified, but since the DATETIME column technique is easier to display on screen and demonstrate when the change was made, I chose it for my sample application. Both of these are solid choices, but I prefer the TIMESTAMP technique since it does not involve any additional code to update its value.

Retrieving Row Flags

One of the keys to implementing concurrency controls is to update the timestamp or datetime field's value back into the DataSet. If the same user wants to make more modifications, this updated value is reflected in the DataSet so it can be used again. There are a few different ways to do this. The fastest is using output parameters within the stored procedure. (This should only return if @@ROWCOUNT equals 1.) The next fastest involves selecting the row again after the UPDATE within the stored procedure. The slowest involves selecting the row from another SQL statement or stored procedure from the SqlDataAdapter's RowUpdated event.

I prefer to use the output parameter technique since it is the fastest and incurs the least overhead. Using the RowUpdated event works well, but it requires me to make a second call from the application to the database. The following code snippet adds an output parameter to the SqlCommand object that is used to update the Employee information:

oUpdCmd.Parameters.Add(new SqlParameter("@NewLastUpdateDateTime",

SqlDbType.DateTime, 8, ParameterDirection.Output,

false, 0, 0, "LastUpdateDateTime", DataRowVersion.Current, null));

oUpdCmd.UpdatedRowSource = UpdateRowSource.OutputParameters;


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The output parameter has its sourcecolumn and sourceversion arguments set to point the output parameter's return value back to the current value of the LastUpdateDateTime column of the DataSet. This way the updated DATETIME value is retrieved and can be returned to the user's .aspx page. Contd....

Saving Changes

Now that the Employees table has the tracking field (LastUpdateDateTime) and the stored procedure has been created to use both the primary key and the tracking field in the WHERE clause of the UPDATE statement, let's take a look at the role of ADO.NET. In order to trap the event when the user changes the values in the textboxes, I created an event handler for the TextChanged event for each TextBox control:

private void txtLastName_TextChanged(object sender, System.EventArgs e)

{

// Get the employee DataRow (there is only 1 row, otherwise I could

// do a Find)

dsEmployee.EmployeeRow oEmpRow =

(dsEmployee.EmployeeRow)oDsEmployee.Employee.Rows[0];

oEmpRow.LastName = txtLastName.Text;

// Save changes back to Session

Session["oDsEmployee"] = oDsEmployee;

}

This event retrieves the row and sets the appropriate field's value from the TextBox. (Another way of getting the changed values is to grab them when the user clicks the Save button.) Each TextChanged event executes after the Page_Load event fires on a postback, so assuming the user changed the first and last names, when the user clicks the Save button, the events could fire in this order: Page_Load, txtFirstName_TextChanged, txtLastName_TextChanged, and btnSave_Click.

The Page_Load event grabs the row from the DataSet in the Session object; the TextChanged events update the DataRow with the new values; and the


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btnSave_Click event attempts to save the record to the database. The btnSave_Click event calls the SaveEmployee method (shown in Figure 3) and passes it a bLastInWins value of false since we want to attempt a standard save first. If the SaveEmployee method detects that changes were made to the row (using the HasChanges method on the DataSet, or alternatively using the RowState property on the row), it creates an instance of the Employee class and passes the DataSet to its SaveEmployee method. The Employee class could live in a logical or physical middle tier. (I wanted to make this a separate class so it would be easy to pull the code out and separate it from the presentation logic.)

Notice that I did not use the GetChanges method to pull out only the modified rows and pass them to the Employee object's Save method. I skipped this step here since there is only one row. However, if there were multiple rows in the DataSet's DataTable, it would be better to use the GetChanges method to create a DataSet that contains only the modified rows.

If the save succeeds, the Employee.SaveEmployee method returns a DataSet containing the modified row and its newly updated row version flag (in this case, the LastUpdateDateTime field's value). This DataSet is then merged into the original DataSet so that the LastUpdateDateTime field's value can be updated in the original DataSet. This must be done because if the user wants to make more changes she will need the current values from the database merged back into the local DataSet and shown on screen. This includes the LastUpdateDateTime value which is used in the WHERE clause. Without this field's current value, a false concurrency violation would occur.

Reporting Violations

If a concurrency violation occurs, it will bubble up and be caught by the exception handler shown in Figure 3 in the catch block for DBConcurrencyException. This block calls the FillConcurrencyValues method, which displays both the original values in the DataSet that were attempted to be saved to the database and the values currently in the database. This method is used merely to show the user why the violation occurred. Notice that the exDBC variable is passed to the FillConcurrencyValues method. This instance of the special database concurrency exception class (DBConcurrencyException) contains the row where the violation occurred. When a concurrency violation occurs, the screen is updated to look like Figure 1.

The DataSet not only stores the schema and the current data, it also tracks changes that have been made to its data. It knows which rows and columns have been


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modified and it keeps track of the before and after versions of these values. When accessing a column's value via the DataRow's indexer, in addition to the column index you can also specify a value using the DataRowVersion enumerator. For example, after a user changes the value of the last name of an employee, the following lines of C# code will retrieve the original and current values stored in the LastName column:

string sLastName_Before = oEmpRow["LastName", DataRowVersion.Original];

string sLastName_After = oEmpRow["LastName", DataRowVersion.Current];

The FillConcurrencyValues method uses the row from the DBConcurrencyException and gets a fresh copy of the same row from the database. It then displays the values using the DataRowVersion enumerators to show the original value of the row before the update and the value in the database alongside the current values in the textboxes.

User's Choice

Once the user has been notified of the concurrency issue, you could leave it up to her to decide how to handle it. Another alternative is to code a specific way to deal with concurrency, such as always handling the exception to let the user know (but refreshing the data from the database). In this sample application I let the user decide what to do next. She can either cancel changes, cancel and reload from the database, save changes, or save anyway.

The option to cancel changes simply calls the RejectChanges method of the DataSet and rebinds the DataSet to the controls in the ASP.NET page. The RejectChanges method reverts the changes that the user made back to its original state by setting all of the current field values to the original field values. The option to cancel changes and reload the data from the database also rejects the changes but additionally goes back to the database via the Employee class in order to get a fresh copy of the data before rebinding to the control on the ASP.NET page.

The option to save changes attempts to save the changes but will fail if a concurrency violation is encountered. Finally, I included a "save anyway" option. This option takes the values the user attempted to save and uses the last-in wins technique, overwriting whatever is in the database. It does this by calling a different command object associated with a stored procedure that only uses the primary key field (EmployeeID) in the WHERE clause of the UPDATE statement. This technique should be used with caution as it will overwrite the record.


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If you want a more automatic way of dealing with the changes, you could get a fresh copy from the database. Then overwrite just the fields that the current user modified, such as the Extension field. That way, in the example I used the proper LastName would not be overwritten. Use this with caution as well, however, because if the same field was modified by both users, you may want to just back out or ask the user what to do next. What is obvious here is that there are several ways to deal with concurrency violations, each of which must be carefully weighed before you decide on the one you will use in your application.

Wrapping It Up

Setting the SqlDataAdapter's ContinueUpdateOnError property tells the SqlDataAdapter to either throw an exception when a concurrency violation occurs or to skip the row that caused the violation and to continue with the remaining updates. By setting this property to false (its default value), it will throw an exception when it encounters a concurrency violation. This technique is ideal when only saving a single row or when you are attempting to save multiple rows and want them all to commit or all to fail.

I have split the topic of concurrency violation management into two parts. Next time I will focus on what to do when multiple rows could cause concurrency violations. I will also discuss how the DataViewRowState enumerators can be used to show what changes have been made to a DataSet.

Q 227. How you will set the datarelation between two columns?

ADO.NET provides DataRelation object to set relation between two columns.It helps to enforce the following constraints,a unique constraint, which guarantees that a column in the table contains no duplicates and a foreign-key constraint,which can be used to maintain referential integrity.A unique constraint is implemented either by simply setting the Unique property of a data column to true, or by adding an instance of the UniqueConstraint class to the DataRelation object's ParentKeyConstraint. As part of the foreign-key constraint, you can specify referential integrity rules that are applied at three points,when a parent record is updated,when a parent record is deleted and when a change is accepted or rejected.


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C# and VB.NET Q 228. Explain the differences between Server-side and Client-side code?

Ans :- Server side code executes on the server.For this to occur page has to be submitted or posted back.Events fired by the controls are executed on the server.Client side code executes in the browser of the client without submitting the page. e.g. In ASP.NET for webcontrols like asp:button the click event of the button is executed on the server hence the event handler for the same in a part of the code-behind (server-side code). Along the server-side code events one can also attach client side events which are executed in the clients browser i.e. javascript events.


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Q 229. How does VB.NET/C# achieve polymorphism?

Ans :- Polymorphism is also achieved through interfaces. Like abstract classes, interfaces also describe the methods that a class needs to implement. The difference between abstract classes and interfaces is that abstract classes always act as a base class of the related classes in the class hierarchy. For example, consider a hierarchy-car and truck classes derived from four-wheeler class; the classes two-wheeler and four-wheeler derived from an abstract class vehicle. So, the class 'vehicle' is the base class in the class hierarchy. On the other hand dissimilar classes can implement one interface. For example, there is an interface that compares two objects. This interface can be implemented by the classes like box, person and string, which are unrelated to each other.

C# allows multiple interface inheritance. It means that a class can implement more than one interface. The methods declared in an interface are implicitly abstract. If a class implements an interface, it becomes mandatory for the class to override all the methods declared in the interface, otherwise the derived class would become abstract.

Can you explain what inheritance is and an example of when you might use it? The savingaccount class has two data members-accno that stores account number, and trans that keeps track of the number of transactions. We can create an object of savingaccount class as shown below.

savingaccount s = new savingaccount ( "Amar", 5600.00f ) ; From the constructor of savingaccount class we have called the two-argument constructor of the account class using the base keyword and passed the name and balance to this constructor using which the data member's name and balance are initialised.

We can write our own definition of a method that already exists in a base class. This is called method overriding. We have overridden the deposit( ) and withdraw( ) methods in the savingaccount class so that we can make sure that each account maintains a minimum balance of Rs. 500 and the total number of transactions do not exceed 10. From these methods we have called the base class's methods to update the balance using the base keyword. We have also overridden the display( ) method to display additional information, i.e. account number.

Working of currentaccount class is more or less similar to that of savingaccount class.


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Using the derived class's object, if we call a method that is not overridden in the derived class, the base class method gets executed. Using derived class's object we can call base class's methods, but the reverse is not allowed.

Unlike C++, C# does not support multiple inheritance. So, in C# every class has exactly one base class. Now, suppose we declare reference to the base class and store in it the address of instance of derived class as shown below.

account a1 = new savingaccount ( "Amar", 5600.00f ) ; account a2 = new currentaccount ( "MyCompany Pvt. Ltd.", 126000.00f) ; Such a situation arises when we have to decide at run-time a method of which class in a class hierarchy should get called. Using a1 and a2, suppose we call the method display( ), ideally the method of derived class should get called. But it is the method of base class that gets called. This is because the compiler considers the type of reference (account in this case) and resolves the method call. So, to call the proper method we must make a small change in our program. We must use the virtual keyword while defining the methods in base class as shown below.

public virtual void display( ) { } We must declare the methods as virtual if they are going to be overridden in derived class. To override a virtual method in derived classes we must use the override keyword as given below.

public override void display( ) { } Now it is ensured that when we call the methods using upcasted reference, it is the derived class's method that would get called. Actually, when we declare a virtual method, while calling it, the compiler considers the contents of the reference rather than its type.

If we don't want to override base class's virtual method, we can declare it with new modifier in derived class. The new modifier indicates that the method is new to this class and is not an override of a base class method.

Q 230. How would you implement inheritance using VB.NET/C#?

Ans :- When we set out to implement a class using inheritance, we must first start with an existing class from which we will derive our new subclass. This existing class, or base class, may be part of the .NET system class library framework, it may be part of some other application or .NET assembly, or we may create it as part of our existing application. Once we have a base class, we can then implement one or


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more subclasses based on that base class. Each of our subclasses will automatically have all of the methods, properties, and events of that base class ? including the implementation behind each method, property, and event. Our subclass can add new methods, properties, and events of its own - extending the original interface with new functionality. Additionally, a subclass can replace the methods and properties of the base class with its own new implementation - effectively overriding the original behavior and replacing it with new behaviors. Essentially inheritance is a way of merging functionality from an existing class into our new subclass. Inheritance also defines rules for how these methods, properties, and events can be merged. In VB.NET we can use implements keyword for inheritance, while in C# we can use the sign ( :: ) between subclass and baseclass.

Q 231. How is a property designated as read-only?

Ans :- VB.NET:

Private mPropertyName as DataType Public ReadOnly Property PropertyName() As DataType Get Return mPropertyName End Get End Property

In C#

Private DataType mPropertyName; public returntype PropertyName { get{ //property implementation goes here return mPropertyName; } // Do not write the set implementation }

Q 232. What is hiding in CSharp ?

Ans :- Hiding is also called as Shadowing. This is the concept of Overriding the methods. It is a concept used in the Object Oriented Programming.


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E.g. public class ClassA { public virtual void MethodA() { Trace.WriteLine("ClassA Method"); } }

public class ClassB : ClassA { public new void MethodA() { Trace.WriteLine("SubClass ClassB Method"); } }

public class TopLevel { static void Main(string[] args) { TextWriter tw = Console.Out; Trace.Listeners.Add(new TextWriterTraceListener(tw)); ClassA obj = new ClassB(); obj.MethodA(); // Outputs �Class A Method" ClassB obj1 = new ClassB(); obj.MethodA(); // Outputs �SubClass ClassB Method� } }

Q 233. What is the difference between an XML "Fragment" and an XML "Document."

Ans :- An XML fragment is an XML document with no single top-level root element. To put it simple it is a part (fragment) of a well-formed xml document. (node) Where as a well-formed xml document must have only one root element.

Q 234. What does it meant to say �the canonical� form of XML?

Ans :- "The purpose of Canonical XML is to define a standard format for an XML document. Canonical XML is a very strict XML syntax, which lets documents in canonical XML be compared directly. Using this strict syntax makes it easier to see whether two XML documents are the


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same. For example, a section of text in one document might read Black & White, whereas the same section of text might read Black & White in another document, and even in another. If you compare those three documents byte by byte, they'll be different. But if you write them all in canonical XML, which specifies every aspect of the syntax you can use, these three documents would all have the same version of this text (which would be Black & White) and could be compared without problem. This Comparison is especially critical when xml documents are digitally signed. The digital signal may be interpreted in different way and the document may be rejected.

Q 235. Why is the XML InfoSet specification different from the Xml DOM? What does the InfoSet attempt to solve?

Ans:- "The XML Information Set (Infoset) defines a data model for XML. The Infoset describes the abstract representation of an XML Document. Infoset is the generalized representation of the XML Document, which is primarily meant to act as a set of definitions used by XML technologies to formally describe what parts of an XML document they operate upon. The Document Object Model (DOM) is one technology for representing an XML Document in memory and to programmatically read, modify and manipulate a xml document. Infoset helps defining generalized standards on how to use XML that is not dependent or tied to a particular XML specification or API. The Infoset tells us what part of XML Document should be considered as significant information.

Q 236. Contrast DTDs versus XSDs. What are their similarities and differences? Which is preferred and why?

Ans :- Document Type Definition (DTD) describes a model or set of rules for an XML document. XML Schema Definition (XSD) also describes the structure of an XML document but XSDs are much more powerful. The disadvantage with the Document Type Definition is it doesn�t support data types beyond the basic 10 primitive types. It cannot properly define the type of data contained by the tag. An Xml Schema provides an Object Oriented approach to defining the format of an xml document. The Xml schema support most basic programming types like integer, byte, string, float etc., We can also define complex types of our own which can be used to define a xml document.


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Xml Schemas are always preferred over DTDs as a document can be more precisely defined using the XML Schemas because of its rich support for data representation.

Q 237. Speaking of Boolean data types, what's different between C# and C/C++?

Ans :- There's no conversion between 0 and false, as well as any other number and true, like in C/C++.

Q 238. How do you convert a string into an integer in .NET?

Ans:- Int32.Parse(string)

Q 239. Can you declare a C++ type destructor in C# like ~MyClass()?

Ans:- Yes, but what's the point, since it will call Finalize(), and Finalize() has no guarantees when the memory will be cleaned up, plus, it introduces additional load on the garbage collector.

Q 240. What's different about namespace declaration when comparing that to package declaration in Java?

Ans :- No semicolon.

Q 241. What's the difference between const and readonly?

Ans :- The readonly keyword is different from the const keyword. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used. Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants as in the following example: public static readonly uint l1 = (uint) DateTime.Now.Ticks;


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Q 242. What does \a character do?

Ans :- On most systems, produces a rather annoying beep.

Q 243. Can you create enumerated data types in C#? Ans :- Yes.

Q 244. What's different about switch statements in C#?

Ans :- No fall-throughs allowed.

Q 245. What happens when you encounter a continue statement inside the for loop?

Ans :- The code for the rest of the loop is ignored, the control is transferred back to the beginning of the loop.


Ans :- By calling Sort() and then Reverse() methods.


Ans :- Yes.

Q 248. What's the C# equivalent of C++ catch (�), which was a catch-all statement for any possible exception?

Ans :- A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.

Q 249.Can multiple catch blocks be executed?


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Ans :- No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.


Ans :- Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.

Q 251. What's the difference between // comments, /* */ comments and /// comments?

Ans :- Single-line, multi-line and XML documentation comments.


Ans :- Compile it with a /doc switch.


Ans :- Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.

Q 254. What's the implicit name of the parameter that gets passed into the class' set method?

Ans :- Value, and it's datatype depends on whatever variable we're changing.

Q 255. How do you inherit from a class in C#?

Ans :- Place a colon and then the name of the base class. Notice that it's double colon in C++.

Q 256. Does C# support multiple inheritance?


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Ans :- No, use interfaces instead.

Q 257. So how do you retrieve the customized properties of a .NET application from XML .config file? Can you automate this process?

Ans :- Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable. In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.

Q 258. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio?

Ans :- The designer will likely through it away, most of the code inside InitializeComponent is auto-generated.

Q 259. Where do you add an event handler?

Ans :- It's the Attributesproperty, the Add function inside that property. e.g. btnSubmit.Attributes.Add(""onMouseOver"",""someClientCode();"")

Q 260. What are jagged array?

Ans :- First lets us answer the question that what an array is? The dictionary meaning of array is an orderly arrangement or sequential arrangement of elements. In computer science term: An array is a data structure that contains a number of variables, which are accessed through computed indices. The variables contained in an array, also called the elements of the array, are all of the same type, and this type is called the element type of the array.

An array has a rank that determines the number of indices associated with each array element. The rank of an array is also referred to as the dimensions of the array. An array with a rank of one is called a single-dimensional array. An array


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with a rank greater than one is called a multi-dimensional array. Specific sized multidimensional arrays are often referred to as two-dimensional arrays, three-dimensional arrays, and so on.

Now let us answer What are jagged arrays? A jagged array is an array whose elements are arrays. The elements of jagged array can be of different dimensions and sizes. A jagged array is sometimes called as �array-of-arrays�. It is called jagged because each of its rows is of different size so the final or graphical representation is not a square.

When you create a jagged array you declare the number of rows in your array. Each row will hold an array that will be on any length. Before filling the values in the inner arrays you must declare them.

Jagged array declaration in C#:

For e.g. : int [] [] myJaggedArray = new int [3][];

Declaration of inner arrays: myJaggedArray[0] = new int[5] ; // First inner array will be of length 5. myJaggedArray[1] = new int[4] ; // Second inner array will be of length 4. myJaggedArray[2] = new int[3] ; // Third inner array will be of length 3.

Now to access third element of second row we write: int value = myJaggedArray[1][2];

Note that while declaring the array the second dimension is not supplied because this you will declare later on in the code.

Jagged array are created out of single dimensional arrays so be careful while using them. Don�t confuse it with multi-dimensional arrays because unlike them jagged arrays are not rectangular arrays.

For more information on arrays: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfarrayspg.asp

Q 261. What is a delegate, why should you use it and how do you call it ?

Ans :- A delegate is a reference type that refers to a Shared method of a type or to an instance method of an object. Delegate is like a function pointer in C and C++.


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Pointers are used to store the address of a thing. Delegate lets some other code call your function without needing to know where your function is actually located. All events in .NET actually use delegates in the background to wire up events. Events are really just a modified form of a delegate. It should give you an idea of some different areas in which delegates may be appropriate:

• They enable callback functionality in multi-tier applications as demonstrated in the examples above. <o:p></o:p>

• The CacheItemRemoveCallback delegate can be used in ASP.NET to keep cached information up to date. When the cached information is removed for any reason, the associated callback is exercised and could contain a reload of the cached information. <o:p></o:p>

• Use delegates to facilitate asynchronous processing for methods that do not offer asynchronous behavior.

• Events use delegates so clients can give the application events to call when the event is fired. Exposing custom events within your applications requires the use of delegates.

Q 262. How does the XmlSerializer work?

Ans :- XmlSerializer in the .NET Framework is a great tool to convert Xml into runtime objects and vice versa

If you define integer variable and a object variable and a structure then how those will be plotted in memory.

Integer , structure � System.ValueType -- Allocated memory on stack , infact integer is primitive type recognized and allocated memory by compiler itself .

Infact , System.Int32 definition is as follows :


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[C#] [Serializable] public struct Int32 : IComparable, IFormattable, IConvertible

So , it�s a struct by definition , which is the same case with various other value types .

Object � Base class , that is by default reference type , so at runtime JIT compiler allocates memory on the �Heap� Data structure .

Reference types are defined as class , derived directly or indirectly by System.ReferenceType WebServices And Windows Services

Can you give an example of when it would be appropriate to use a web service as opposed to non-serviced .NET component Web service is one of main component in Service Oriented Architecture. You could use web services when your clients and servers are running on different networks and also different platforms. This provides a loosely coupled system. And also if the client is behind the firewall it would be easy to use web service since it runs on port 80 (by default) instead of having some thing else in Service Oriented Architecture applications. What is the standard you use to wrap up a call to a Web service "SOAP. " Q 263. What is the transport protocol you use to call a Web service SOAP? Ans :- HTTP with SOAP Q 264. What does WSDL stand for? Ans :- "WSDL stands for Web Services Dsescription Langauge. There is WSDL.exe that creates a .wsdl Files which defines how an XML Web service behaves and instructs clients as to how to interact with the service. eg: wsdl http://LocalHost/WebServiceName.asmx" Q 265. Where on the Internet would you look for Web Services? Ans :- www.uddi.org Q 267. What does WSDL stand for?


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Ans :- Web Services Description Language Q 268. True or False: To test a Web service you must create a windows application or Web application to consume this service? Ans :- False. Q 269. What are the various ways of accessing a web service ? Ans :- 1.Asynchronous Call Application can make a call to the Webservice and then continue todo watever oit wants to do.When the service is ready it will notify the application.Application can use BEGIN and END method to make asynchronous call to the webmethod.We can use either a WaitHandle or a Delegate object when making asynchronous call. The WaitHandle class share resources between several objects. It provides several methods which will wait for the resources to become available The easiest and most powerful way to to implement an asynchronous call is using a delegate object. A delegate object wraps up a callback function. The idea is to pass a method in the invocation of the web method. When the webmethod has finished it will call this callback function to process the result 2.Synchronous Call Application has to wait until execution has completed. Q 270. What are VSDISCO files? Ans :- VSDISCO files are DISCO files that support dynamic discovery of Web services. If you place the following VSDISCO file in a directory on your Web server, for example, it returns references to all ASMX and DISCO files in the host directory and any subdirectories not noted in <EXCLUDE>elements: <DYNAMICDISCOVERY xmlns="urn:schemas-dynamicdiscovery:disco.2000-03-17"> <EXCLUDE path="_vti_cnf" />


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<EXCLUDE path="_vti_pvt" /> <EXCLUDE path="_vti_log" /> <EXCLUDE path="_vti_script" /> <EXCLUDE path="_vti_txt" /> </DYNAMICDISCOVERY> Q 271. How does dynamic discovery work? Ans :- ASP.NET maps the file name extension VSDISCO to an HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document. Note that VSDISCO files are disabled in the release version of ASP.NET. You can reenable them by uncommenting the line in the <HTTPHANDLERS>section of Machine.config that maps *.vsdisco to System.Web.Services.Discovery.DiscoveryRequestHandler and granting the ASPNET user account permission to read the IIS metabase. However, Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security. Q 272. Is it possible to prevent a browser from caching an ASPX page? Ans :- Just call SetNoStore on the HttpCachePolicy object exposed through the Response object's Cache property, as demonstrated here: <%@ Page Language="C#" %> <% Response.Cache.SetNoStore (); Response.Write (DateTime.Now.ToLongTimeString ()); %> SetNoStore works by returning a Cache-Control: private, no-store header in the HTTP response. In this example, it prevents caching of a Web page that shows the current time. Q 273. What does AspCompat="true" mean and when should I use it?


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Ans :- AspCompat is an aid in migrating ASP pages to ASPX pages. It defaults to false but should be set to true in any ASPX file that creates apartment-threaded COM objects--that is, COM objects registered ThreadingModel=Apartment. That includes all COM objects written with Visual Basic 6.0. AspCompat should also be set to true (regardless of threading model) if the page creates COM objects that access intrinsic ASP objects such as Request and Response. The following directive sets AspCompat to true: <%@ Page AspCompat="true" %> Setting AspCompat to true does two things. First, it makes intrinsic ASP objects available to the COM components by placing unmanaged wrappers around the equivalent ASP.NET objects. Second, it improves the performance of calls that the page places to apartment- threaded COM objects by ensuring that the page (actually, the thread that processes the request for the page) and the COM objects it creates share an apartment. AspCompat="true" forces ASP.NET request threads into single-threaded apartments (STAs). If those threads create COM objects marked ThreadingModel=Apartment, then the objects are created in the same STAs as the threads that created them. Without AspCompat="true," request threads run in a multithreaded apartment (MTA) and each call to an STA-based COM object incurs a performance hit when it's marshaled across apartment boundaries. Do not set AspCompat to true if your page uses no COM objects or if it uses COM objects that don't access ASP intrinsic objects and that are registered ThreadingModel=Free or ThreadingModel=Both. Q 274. Can two different programming languages be mixed in a single ASMX file? Ans :- No. Q 275. What namespaces are imported by default in ASMX files? Ans :- The following namespaces are imported by default. Other namespaces must be imported manually.· System, System.Collections,System.ComponentModel,System.Data, System.Diagnostics,System.Web,System.Web.Services How do I provide information to the Web Service when the information is required as a SOAP Header? The key here is the Web Service proxy you created using wsdl.exe or through Visual Studio .NET's Add Web Reference menu option. If you happen to download a WSDL file for a Web Service that requires a SOAP header, .NET will create a SoapHeader


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class in the proxy source file. Using the previous example: public class Service1 : System.Web.Services.Protocols.SoapHttpClientProtocol { public AuthToken AuthTokenValue; [System.Xml.Serialization.XmlRootAttribute(Namespace="http://tempuri.org/", IsNullable=false)] public class AuthToken : SoapHeader { public string Token; }} In this case, when you create an instance of the proxy in your main application file, you'll also create an instance of the AuthToken class and assign the string: Service1 objSvc = new Service1(); processingobjSvc.AuthTokenValue = new AuthToken(); objSvc.AuthTokenValue.Token = <ACTUAL token value>; Web Servicestring strResult = objSvc.MyBillableWebMethod(); Q 276. What is WSDL? Ans :- WSDL is the Web Service Description Language, and it is implemented as a specific XML vocabulary. While it's very much more complex than what can be described here, there are two important aspects to WSDL with which you should be aware. First, WSDL provides instructions to consumers of Web Services to describe the layout and contents of the SOAP packets the Web Service intends to issue. It's an interface description document, of sorts. And second, it isn't intended that you read and interpret the WSDL. Rather, WSDL should be processed by machine, typically to generate proxy source code (.NET) or create dynamic proxies on the fly (the SOAP Toolkit or Web Service Behavior). Q 277. What is a Windows Service and how does its lifecycle differ from a "standard" EXE? Ans :- Windows service is a application that runs in the background. It is equivalent to a NT service. The executable created is not a Windows application, and hence you can't just click and run it . it needs to be installed as a service, VB.Net has a facility where we can add an installer to our program and then use a utility to install the service. Where as this is not the case with standard exe Q 278. How can a win service developed in .NET be installed or used in Win98?


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Ans:- Windows service cannot be installed on Win9x machines even though the .NET framework runs on machine. Q 279. Can you debug a Windows Service? How ? Ans :- Yes we can debug a Windows Service. Attach the WinDbg debugger to a service after the service starts This method is similar to the method that you can use to attach a debugger to a process and then debug a process. Use the process ID of the process that hosts the service that you want to debug 1 To determine the process ID (PID) of the process that hosts the service that you want to debug, use one of the following methods. � Method 1: Use the Task Manager a. Right-click the taskbar, and then click Task Manager. The Windows Task Manager dialog box appears. b. Click the Processes tab of the Windows Task Manager dialog box. c. Under Image Name, click the image name of the process that hosts the service that you want to debug. Note the process ID of this process as specified by the value of the corresponding PID field. � Method 2: Use the Task List Utility (tlist.exe) a. Click Start, and then click Run. The Run dialog box appears. b. In the Open box, type cmd, and then click OK. c. At the command prompt, change the directory path to reflect the location of the tlist.exe file on your computer. Note The tlist.exe file is typically located in the following directory: C:\Program Files\Debugging Tools for Windows d. At the command prompt, type tlist to list the image names and the process IDs of all processes that are currently running on your computer. Note Make a note of the process ID of the process that hosts the service that you want to debug. 2 At a command prompt, change the directory path to reflect the location of the windbg.exe file on your computer. Note If a command prompt is not open, follow steps a and b of Method 1. The windbg.exe file is typically located in the following directory: C:\Program Files\Debugging Tools for Windows. 3 At the command prompt, type windbg �p ProcessID to attach the WinDbg


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debugger to the process that hosts the service that you want to debug. Note ProcessID is a placeholder for the process ID of the process that hosts the service that you want to debug. Use the image name of the process that hosts the service that you want to debug You can use this method only if there is exactly one running instance of the process that hosts the service that you want to run. To do this, follow these steps: 1 Click Start, and then click Run. The Run dialog box appears. 2 In the Open box, type cmd, and then click OK to open a command prompt. 3 At the command prompt, change the directory path to reflect the location of the windbg.exe file on your computer. Note The windbg.exe file is typically located in the following directory: C:\Program Files\Debugging Tools for Windows. 4 At the command prompt, type windbg �pn ImageName to attach the WinDbg debugger to the process that hosts the service that you want to debug. NoteImageName is a placeholder for the image name of the process that hosts the service that you want to debug. The "-pn" command-line option specifies that the ImageName command-line argument is the image name of a process. back to the top Start the WinDbg debugger and attach to the process that hosts the service that you want to debug 1 Start Windows Explorer. 2 Locate the windbg.exe file on your computer. Note The windbg.exe file is typically located in the following directory: C:\Program Files\Debugging Tools for Windows 3 Run the windbg.exe file to start the WinDbg debugger. 4 On the File menu, click Attach to a Process to display the Attach to Process dialog box. 5 Click to select the node that corresponds to the process that hosts the service that you want to debug, and then click OK. 6 In the dialog box that appears, click Yes to save base workspace information. Notice that you can now debug the disassembled code of your service. Configure a service to start with the WinDbg debugger attached You can use this method to debug services if you want to troubleshoot service-


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startup-related problems. 1 Configure the "Image File Execution" options. To do this, use one of the following methods: � Method 1: Use the Global Flags Editor (gflags.exe) a. Start Windows Explorer. b. Locate the gflags.exe file on your computer. Note The gflags.exe file is typically located in the following directory: C:\Program Files\Debugging Tools for Windows. c. Run the gflags.exe file to start the Global Flags Editor. d. In the Image File Name text box, type the image name of the process that hosts the service that you want to debug. For example, if you want to debug a service that is hosted by a process that has MyService.exe as the image name, type MyService.exe. e. Under Destination, click to select the Image File Options option. f. Under Image Debugger Options, click to select the Debugger check box. g. In the Debugger text box, type the full path of the debugger that you want to use. For example, if you want to use the WinDbg debugger to debug a service, you can type a full path that is similar to the following: C:\Program Files\Debugging Tools for Windows\windbg.exe h. Click Apply, and then click OK to quit the Global Flags Editor. � Method 2: Use Registry Editor a. Click Start, and then click Run. The Run dialog box appears. b. In the Open box, type regedit, and then click OK to start Registry Editor. c. Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk. In Registry Editor, locate, and then right-click the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options d. Point to New, and then click Key. In the left pane of Registry Editor, notice that New Key #1 (the name of a new registry subkey) is selected for editing. e. Type ImageName to replace New Key #1, and then press ENTER. Note ImageName is a placeholder for the image name of the process that hosts the service that you want to debug. For example, if you want to debug a service that is hosted by a process that has MyService.exe as the image name, type MyService.exe. f. Right-click the registry subkey that you created in step e.


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g. Point to New, and then click String Value. In the right pane of Registry Editor, notice that New Value #1, the name of a new registry entry, is selected for editing. h. Replace New Value #1 with Debugger, and then press ENTER. i. Right-click the Debugger registry entry that you created in step h, and then click Modify. The Edit String dialog box appears. j. In the Value data text box, type DebuggerPath, and then click OK. Note DebuggerPath is a placeholder for the full path of the debugger that you want to use. For example, if you want to use the WinDbg debugger to debug a service, you can type a full path that is similar to the following: C:\Program Files\Debugging Tools for Windows\windbg.exe 2 For the debugger window to appear on your desktop, and to interact with the debugger, make your service interactive. If you do not make your service interactive, the debugger will start but you cannot see it and you cannot issue commands. To make your service interactive, use one of the following methods: � Method 1: Use the Services console a. Click Start, and then point to Programs. b. On the Programs menu, point to Administrative Tools, and then click Services. The Services console appears. c. In the right pane of the Services console, right-click ServiceName, and then click Properties. Note ServiceName is a placeholder for the name of the service that you want to debug. d. On the Log On tab, click to select the Allow service to interact with desktop check box under Local System account, and then click OK. � Method 2: Use Registry Editor a. In Registry Editor, locate, and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ServiceName Note Replace ServiceName with the name of the service that you want to debug. For example, if you want to debug a service named MyService, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MyService b. Under the Name field in the right pane of Registry Editor, right-click Type, and then click Modify. The Edit DWORD Value dialog box appears. c. Change the text in the Value data text box to the result of the binary OR operation with the binary value of the current text and the binary value, 0x00000100, as the two operands. The binary value, 0x00000100, corresponds to the SERVICE_INTERACTIVE_PROCESS constant that is defined in the WinNT.h header file on your computer. This constant specifies that a service is interactive in


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nature. 3 When a service starts, the service communicates to the Service Control Manager how long the service must have to start (the time-out period for the service). If the Service Control Manager does not receive a "service started" notice from the service within this time-out period, the Service Control Manager terminates the process that hosts the service. This time-out period is typically less than 30 seconds. If you do not adjust this time-out period, the Service Control Manager ends the process and the attached debugger while you are trying to debug. To adjust this time-out period, follow these steps: a. In Registry Editor, locate, and then right-click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control b. Point to New, and then click DWORD Value. In the right pane of Registry Editor, notice that New Value #1 (the name of a new registry entry) is selected for editing. c. Type ServicesPipeTimeout to replace New Value #1, and then press ENTER. d. Right-click the ServicesPipeTimeout registry entry that you created in step c, and then click Modify. The Edit DWORD Value dialog box appears. e. In the Value data text box, type TimeoutPeriod, and then click OK Note TimeoutPeriod is a placeholder for the value of the time-out period (in milliseconds) that you want to set for the service. For example, if you want to set the time-out period to 24 hours (86400000 milliseconds), type 86400000. f. Restart the computer. You must restart the computer for Service Control Manager to apply this change. 4 Start your Windows service. To do this, follow these steps: a. Click Start, and then point to Programs. b. On the Programs menu, point to Administrative Tools, and then click Services. The Services console appears. c. In the right pane of the Services console, right-click ServiceName, and then click Start. Note ServiceName is a placeholder for the name of the service that you want to debug.


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COM And COM+ Q 280. What are different transaction options available for services components ?

Ans :- There are 5 transactions types that can be used with COM+. Whenever an object is registered with COM+ it has to abide either to these 5 transaction types.


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Disabled: - There is no transaction. COM+ does not provide transaction support for this component.

Not Supported: - Component does not support transactions. Hence even if the calling component in the hierarchy is transaction enabled this component will not participate in the transaction.

Supported: - Components with transaction type supported will be a part of the transaction if the calling component has an active transaction. If the calling component is not transaction enabled this component will not start a new transaction.

Required: - Components with this attribute require a transaction i.e. either the calling should have a transaction in place else this component will start a new transaction.

Required New: - Components enabled with this transaction type always require a new transaction. Components with required new transaction type instantiate a new transaction for themselves every time.

Q 281. Can we use com Components in .net?.How ?.can we use .net components in vb?.Explain how ?

Ans:- COM components have different internal architecture from .NET components hence they are not innately compatible. However .NET framework supports invocation of unmanaged code from managed code (and vice-versa) through COM/.NET interoperability. .NET application communicates with a COM component through a managed wrapper of the component called Runtime Callable Wrapper (RCW); it acts as managed proxy to the unmanaged COM component. When a method call is made to COM object, it goes onto RCW and not the object itself. RCW manages the lifetime management of the COM component. Implementation Steps -

Create Runtime Callable Wrapper out of COM component. Reference the metadata assembly Dll in the project and use its methods & properties RCW can be created using Type Library Importer utility or through VS.NET. Using VS.NET, add reference through COM tab to select the desired DLL. VS.NET automatically generates metadata assembly putting the classes provided by that component into a namespace with the same name as COM dll (XYZRCW.dll)


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.NET components can be invoked by unmanaged code through COM Callable Wrapper (CCW) in COM/.NET interop. The unmanaged code will talk to this proxy, which translates call to managed environment. We can use COM components in .NET through COM/.NET interoperability. When managed code calls an unmanaged component, behind the scene, .NET creates proxy called COM Callable wrapper (CCW), which accepts commands from a COM client, and forwards it to .NET component. There are two prerequisites to creating .NET component, to be used in unmanaged code: 1. .NET class should be implement its functionality through interface. First define interface in code, then have the class to imlpement it. This way, it prevents breaking of COM client, if/when .NET component changes.

2.Secondly, .NET class, which is to be visible to COM clients must be declared public. The tools that create the CCW only define types based on public classes. The same rule applies to methods, properties, and events that will be used by COM clients.

Implementation Steps - 1. Generate type library of .NET component, using TLBExporter utility. A type library is the COM equivalent of the metadata contained within a .NET assembly. Type libraries are generally contained in files with the extension .tlb. A type library contains the necessary information to allow a COM client to determine which classes are located in a particular server, as well as the methods, properties, and events supported by those classes. 2. Secondly, use Assembly Registration tool (regasm) to create the type library and register it. 3. Lastly install .NET assembly in GAC, so it is available as shared assembly.

Q 282. What is Runtime Callable wrapper?.when it will created?.

Ans :- The common language runtime exposes COM objects through a proxy called the runtime callable wrapper (RCW). Although the RCW appears to be an ordinary object to .NET clients, its primary function is to marshal calls between a .NET client and a COM object. This wrapper turns the COM interfaces exposed by the COM component into .NET-compatible interfaces. For oleautomation (attribute indicates that an interface is compatible with Automation) interfaces, the RCW can be generated automatically from a type library. For non-oleautomation interfaces, it


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may be necessary to develop a custom RCW which manually maps the types exposed by the COM interface to .NET-compatible types.

Q 283. What is Com Callable wrapper?when it will created? Ans :- .NET components are accessed from COM via a COM Callable Wrapper (CCW). This is similar to a RCW, but works in the opposite direction. Again, if the wrapper cannot be automatically generated by the .NET development tools, or if the automatic behaviour is not desirable, a custom CCW can be developed. Also, for COM to 'see' the .NET component, the .NET component must be registered in the registry.CCWs also manage the object identity and object lifetime of the managed objects they wrap.

Q 284. What is a primary interop ?

Ans:- A primary interop assembly is a collection of types that are deployed, versioned, and configured as a single unit. However, unlike other managed assemblies, an interop assembly contains type definitions (not implementation) of types that have already been defined in COM. These type definitions allow managed applications to bind to the COM types at compile time and provide information to the common language runtime about how the types should be marshaled at run time.

Q 285. What are tlbimp and tlbexp tools used for ?

Ans :- The Type Library Exporter generates a type library that describes the types defined in a common language runtime assembly. The Type Library Importer converts the type definitions found within a COM type library into equivalent definitions in a common language runtime assembly. The output of Tlbimp.exe is a binary file (an assembly) that contains runtime metadata for the types defined within the original type library.

Q 286. What benefit do you get from using a Primary Interop Assembly (PIA)?

Ans :- PIAs are important because they provide unique type identity. The PIA distinguishes the official type definitions from counterfeit definitions provided by other interop assemblies. Having a single type identity ensures type compatibility between applications that share the types defined in the PIA. Because the PIA is signed by its publisher and labeled with the PrimaryInteropAssembly attribute, it can be differentiated from other interop assemblies that define the same types.


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Remoting FAQ's Q 287. What distributed process frameworks outside .NET do you know? Ans :- Distributed Computing Environment/Remote Procedure Calls (DEC/RPC), Microsoft Distributed Component Object Model (DCOM), Common Object Request Broker Architecture (CORBA), and Java Remote Method Invocation (RMI). Q 288. What are possible implementations of distributed applications in .NET?


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Ans :- .NET Remoting and ASP.NET Web Services. If we talk about the Framework Class Library, noteworthy classes are in System.Runtime.Remoting and System.Web.Services. Q 289. When would you use .NET Remoting and when Web services? Ans :- Use remoting for more efficient exchange of information when you control both ends of the application. Use Web services for open-protocol-based information exchange when you are just a client or a server with the other end belonging to someone else. Q 290. What's a proxy of the server object in .NET Remoting? Ans :- It's a fake copy of the server object that resides on the client side and behaves as if it was the server. It handles the communication between real server object and the client object. This process is also known as marshaling. Q 291. What are remotable objects in .NET Remoting? Ans :- Remotable objects are the objects that can be marshaled across the application domains. You can marshal by value, where a deep copy of the object is created and then passed to the receiver. You can also marshal by reference, where just a reference to an existing object is passed. Q 292. What are channels in .NET Remoting? Ans :- Channels represent the objects that transfer the other serialized objects from one application domain to another and from one computer to another, as well as one process to another on the same box. A channel must exist before an object can be transferred. Q 293. What security measures exist for .NET Remoting in System.Runtime.Remoting? Ans :- None. Security should be taken care of at the application level. Cryptography and other security techniques can be applied at application or server level. Q 294. What is a formatter? Ans :- A formatter is an object that is responsible for encoding and serializing data


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into messages on one end, and deserializing and decoding messages into data on the other end. Q 295. Choosing between HTTP and TCP for protocols and Binary and SOAP for formatters, what are the trade-offs? Ans :- Binary over TCP is the most effiecient, SOAP over HTTP is the most interoperable. Q 296. What's SingleCall activation mode used for? Ans :- If the server object is instantiated for responding to just one single request, the request should be made in SingleCall mode. Q 297 .What's Singleton activation mode? Ans :- A single object is instantiated regardless of the number of clients accessing it. Lifetime of this object is determined by lifetime lease. Q 298. How do you define the lease of the object? Ans :- By implementing ILease interface when writing the class code. Q 299. Can you configure a .NET Remoting object via XML file? Ans :- Yes, via machine.config and application level .config file (or web.config in ASP.NET). Application-level XML settings take precedence over machine.config. Q 300. How can you automatically generate interface for the remotable object in .NET with Microsoft tools? Ans :- Use the Soapsuds tool. Q 201. What are CAO's i.e. Client Activated Objects ? Ans :- Client-activated objects are objects whose lifetimes are controlled by the calling application domain, just as they would be if the object were local to the client. With client activation, a round trip to the server occurs when the client tries to create an instance of the server object, and the client proxy is created using an object


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reference (ObjRef) obtained on return from the creation of the remote object on the server. Each time a client creates an instance of a client-activated type, that instance will service only that particular reference in that particular client until its lease expires and its memory is recycled. If a calling application domain creates two new instances of the remote type, each of the client references will invoke only the particular instance in the server application domain from which the reference was returned. In COM, clients hold an object in memory by holding a reference to it. When the last client releases its last reference, the object can delete itself. Client activation provides the same client control over the server object's lifetime, but without the complexity of maintaining references or the constant pinging to confirm the continued existence of the server or client. Instead, client-activated objects use lifetime leases to determine how long they should continue to exist. When a client creates a remote object, it can specify a default length of time that the object should exist. If the remote object reaches its default lifetime limit, it contacts the client to ask whether it should continue to exist, and if so, for how much longer. If the client is not currently available, a default time is also specified for how long the server object should wait while trying to contact the client before marking itself for garbage collection. The client might even request an indefinite default lifetime, effectively preventing the remote object from ever being recycled until the server application domain is torn down. The difference between this and a server-activated indefinite lifetime is that an indefinite server-activated object will serve all client requests for that type, whereas the client-activated instances serve only the client and the reference that was responsible for their creation. For more information, see Lifetime Leases. To create an instance of a client-activated type, clients either configure their application programmatically (or using a configuration file) and call new (New in Visual Basic), or they pass the remote object's configuration in a call to Activator.CreateInstance. The following code example shows such a call, assuming a TcpChannel has been registered to listen on port 8080. Q 302. How many processes can listen on a single TCP/IP port? Ans :- One. Q 303. What technology enables out-of-proc communication in .NET? Ans :- Most usually Remoting;.NET remoting enables client applications to use objects in other processes on the same computer or on any other computer available


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on its network.While you could implement an out-of-proc component in any number of other ways, someone using the term almost always means Remoting. Q 304. How can objects in two diff. App Doimains communicate with each other? Ans :- .Net framework provides various ways to communicate with objects in different app domains. First is XML Web Service on internet, its good method because it is built using HTTP protocol and SOAP formatting. If the performance is the main concern then go for second option which is .Net remoting because it gives you the option of using binary encoding and the default TcpChannel, which offers the best interprocess communication performance Q 305. What is the difference between .Net Remoting and Web Services? Ans :- Although we can develop an application using both technologies, each of them has its distinct advantages. Yes you can look at them in terms of performance but you need to consider your need first. There are many other factors such authentications, authorizing in process that need to be considered. Point Remoting Webservices If your application needs interoperability with other platforms or operating systems

No Yes, Choose Web Services because it is more flexible in that they are support SOAP.

If performance is the main requirement with security

You should use the TCP channel and the binary formatter

No

Complex Programming Yes No

State Management

Supports a range of state management, depending on what object lifetime scheme you choose (single call or singleton call).

Its stateless service management (does not inherently correlate multiple calls from the same user)

Transport Protocol It can access through TCP or HTTP channel.

It can be access only through HTTP channel.


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WinForms FAQ : Q 306. What base class do all Web Forms inherit from? Ans :- System.Windows.Forms.Form Q 307. What is the difference between Debug.Write and Trace.Write? When should each be used? Ans :- The Debug.Write call won't be compiled when the DEBUGsymbol is not


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defined (when doing a release build). Trace.Write calls will be compiled. Debug.Write is for information you want only in debug builds, Trace.Write is for when you want it in release build as well. Q 308. Difference between Anchor and Dock Properties? Ans :- Dock Property->Gets or sets which edge of the parent container a control is docked to. A control can be docked to one edge of its parent container or can be docked to all edges and fill the parent container. For example, if you set this property to DockStyle.Left, the left edge of the control will be docked to the left edge of its parent control. Additionally, the docked edge of the control is resized to match that of its container control. Anchor Property->Gets or sets which edges of the control are anchored to the edges of its container. A control can be anchored to one or more edges of its parent container. Anchoring a control to its parent ensures that the anchored edges remain in the same position relative to the edges of the parent container when the parent container is resized. Q 309. When would you use ErrorProvider control? Ans :- ErrorProvider control is used in Windows Forms application. It is like Validation Control for ASP.NET pages. ErrorProvider control is used to provide validations in Windows forms and display user friendly messages to the user if the validation fails. E.g If we went to validate the textBox1 should be empty, then we can validate as below 1). You need to place the errorprovide control on the form private void textBox1_Validating(object sender, System.ComponentModel.CancelEventArgs e) { ValidateName(); } private bool ValidateName() { bool bStatus = true; if (textBox1.Text == "") { errorProvider1.SetError (textBox1,"Please enter your Name"); bStatus = false;


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} else errorProvider1.SetError (textBox1,""); return bStatus; } it check the textBox1 is empty . If it is empty, then a message Please enter your name is displayed. Q 310. Can you write a class without specifying namespace? Which namespace does it belong to by default? Ans :- Yes, you can, then the class belongs to global namespace which has no name. For commercial products, naturally, you wouldn't want global namespace. Q 311. You are designing a GUI application with a windows and several widgets on it. The user then resizes the app window and sees a lot of grey space, while the widgets stay in place. What's the problem? Ans :- One should use anchoring for correct resizing. Otherwise the default property of a widget on a form is top-left, so it stays at the same location when resized. Q 312. How can you save the desired properties of Windows Forms application? Ans :- .config files in .NET are supported through the API to allow storing and retrieving information. They are nothing more than simple XML files, sort of like what .ini files were before for Win32 apps. Q 313. So how do you retrieve the customized properties of a .NET application from XML .config file? Ans :- Initialize an instance of AppSettingsReader class. Call the GetValue method of AppSettingsReader class, passing in the name of the property and the type expected. Assign the result to the appropriate variable. Q 314.Can you automate this process? Ans:- In Visual Studio yes, use Dynamic Properties for automatic .config creation, storage and retrieval.


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Q 315. My progress bar freezes up and dialog window shows blank, when an intensive background process takes over.? Ans :- Yes, you should've multi-threaded your GUI, with taskbar and main form being one thread, and the background process being the other. Q 316. What's the safest way to deploy a Windows Forms app? Ans:- Web deployment: the user always downloads the latest version of the code, the program runs within security sandbox, properly written app will not require additional security privileges. Q 317. Why is it not a good idea to insert code into InitializeComponent method when working with Visual Studio? Ans :- The designer will likely through it away, most of the code inside InitializeComponent is auto-generated. Q 318. What's the difference between WindowsDefaultLocation and WindowsDefaultBounds? Ans :- WindowsDefaultLocation tells the form to start up at a location selected by OS, but with internally specified size. WindowsDefaultBounds delegates both size and starting position choices to the OS. Q 319. What's the difference between Move and LocationChanged? Resize and SizeChanged? Ans :- Both methods do the same, Move and Resize are the names adopted from VB to ease migration to C#. Q 320. How would you create a non-rectangular window, let's say an ellipse? Ans :- Create a rectangular form, set the TransparencyKey property to the same value as BackColor, which will effectively make the background of the form transparent. Then set the FormBorderStyle to FormBorderStyle.None, which will remove the contour and contents of the form. Q 321. How do you create a separator in the Menu Designer?


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Ans:- A hyphen '-' would do it. Also, an ampersand '&\' would underline the next letter. Q 322. How's anchoring different from docking? Ans;- Anchoring treats the component as having the absolute size and adjusts its location relative to the parent form. Docking treats the component location as absolute and disregards the component size. So if a status bar must always be at the bottom no matter what, use docking. If a button should be on the top right, but change its position with the form being resized, use anchoring. Q 323.How do you trigger the Paint event in System.Drawing? Ans:- Invalidate the current form, the OS will take care of repainting. The Update method forces the repaint. Q 324. With these events, why wouldn't Microsoft combine Invalidate and Paint, so that you wouldn't have to tell it to repaint, and then to force it to repaint? Ans:- Painting is the slowest thing the OS does, so usually telling it to repaint, but not forcing it allows for the process to take place in the background. Q 325. How can you assign an RGB color to a System.Drawing.Color object? Ans:- Call the static method FromArgb of this class and pass it the RGB values. Q 326.What class does Icon derive from? Ans:-Isn't it just a Bitmap with a wrapper name around it? No, Icon lives in System.Drawing namespace. It's not a Bitmap by default, and is treated separately by .NET. However, you can use ToBitmap method to get a valid Bitmap object from a valid Icon object. Q 327. Before in my VB app I would just load the icons from DLL. How can I load the icons provided by .NET dynamically? Ans:- By using System.Drawing.SystemIcons class, for example System.Drawing.SystemIcons.Warning produces an Icon with a warning sign in it.


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Q 328. When displaying fonts, what's the difference between pixels, points and ems? Ans:- A pixel is the lowest-resolution dot the computer monitor supports. Its size depends on user's settings and monitor size. A point is always 1/72 of an inch. An em is the number of pixels that it takes to display the letter M. Dear Readers ! Your comments on the contents are highly appreciated. Please e-mail

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