c# (csharp) basic definitions

Microsoft .Net success Kit

• Success Kit

• C# Questions?

• What is a class?

• Blue print of an object. It is programmer defined datatype.It can be public, private, protected.

• What is object?

• It is a specific instance of a class, we are using “new” keyword when we create an object Ex. car c=new car ();

• What is static member variable and methods?

• It means belongs to a class rather than to an object.

• What are the Oops features?

• a).Encapsulation: Hiding some features from outside world. We are using excess modified like Private, Public, and Protected.

• b).Pollymorphism: many forms of methods/classes.

• Ex. Overloaded method.

• Here we can assign subclass object to a super class object.

• c).Inheritance: It is process by which sub class inherits member variable & methods from super class.

• d).Abstraction: It is hiding, providing the interface to the user.• Ex. Object.

• What Is Value Type?

• Just values in the memory are stored in a class

• Ex.int, char & struct.

• What is Reference Type?• Contain the address of the object are stored in attack.

• Ex. Class, interfaces, array & strings.

• What is constructor?

• ->It helps in creating an instance of a class?

• ->Have no return type, not even void.

• ->Can be private, public/procted.• ->Can be overloaded.

• Access Modifier.

• Private->It access within the class.

• Protected->it access within the class & any subclass of that class.

• Public->It excess by all.

• Abstract Method.

• Abstract method is a keyword, which contain abstract method of abstract class.

• Abstract class:-Which contain abstract methods.

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• ->abstract class can not be instantied.

• ->Wee using abstract keyword, when we declare a abstract class.• Ex.Public abstract class car• {

• }

• What is Method Overloading?

• It means same method name & different signature.• ->• They can be in the same class/different class.• ->Public class Adding numbers

• {Public int add (int a, int b)• {• Return a+b;• }

• Public int Add (int a, int b,int c)• {• Return a+b+c;• }• }

• What is method overriding?

• It means same method name & same signature.• ->They can not be in the same class.• ->It has to be in the subclass.• ->Static method can not be overridden.• ->Exception can be same or more.

• ->Excess modified can be same or more.• ->Method overriding is done by the ‘virtual’ keyword.

• What is Boxing & unboxing?• Boxing->When storing value type in the form of object type in the heap

memory(value type into reference type)• UnBoxing->When you are converting object type in the form of value

type(reference type into value type).

• What is an Interface?

• An interface is just like class but not a class, which contains any abstract method & member variable, should be final/static. It is an entity that is defined by the word Interface. An interface has

• No implementation; it only has the signature or in other words, just the definition of the

• Methods without the body. As one of the similarities to abstract class, it is a contract that is

• Used to define hierarchies for all subclasses or it defines specific set of methods and their

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• Arguments. The main difference between them is that a class can implement more than one

• Interface but can only inherit from one abstract class. Since C# doesn’t support multiple

• Inheritance, interfaces are used to implement multiple inheritance.• How do you turn off cookies for one page in your site?• Use the Cookie. Discard Property which 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 users hard disk when a session ends.• Or• it can be turned off by mentioning cookie state= false in web.config file• 16.What is the difference between Convert.ToInt32(string) and

Int32.Parse(string)?• The two give identical results, except where the string is null.

Convert.ToInt32(null) returns zero, whereas Int32.Parse(null) throws an ArgumentNullException.

• 17.What are Destructors?• A destructor is opposite to s constructor. It is called when an object is

no more required. The name of the destructor is the same as the class name and is preceded by a tilde(~) sign. Like constructors, a destructor has no return type.

• C# manages the memory dynamically and uses a garbage collector, running on a separate thread, to execute all destructors on exit. The process of calling a destructor when an object is reclaimed by the garbage collector is called finalization.

• Note: Destructor takes no arguments.

• 18. How u can create XML file?• To write Dataset Contents out to disk as an XML file use:

• MyDataset.WriteXML (server.MapPath ("MyXMLFile.xml"))

• 19. What is CLR?• CLR is .NET equivalent of Java Virtual Machine (JVM). It is the runtime

that converts a MSIL code• into the host machine language code, which is then executed

appropriately. The CLR is the• execution engine for .NET Framework applications. It provides a number

of services, including:• Code management (loading and execution)• Application memory isolation• Verification of type safety• Conversion of IL to native code.• Access to metadata (enhanced type information)• Managing memory for managed objects• Enforcement of code access security

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• Exception handling, including cross-language exceptions• Interoperation between managed code, COM objects, and pre-existing

DLL's (unmanaged code• And data)• Automation of object layout• Support for developer• Services (profiling, debugging, and so on).

• 20. Which two properties are on every validation control?• Control to validate & Error Message.

• 21. What Is The Difference Between View State and Session State?

• View State persist the values of controls of particular page in the client (browser) when post

• Back operation done. When user requests another page previous page data no longer available.

• Session State persist the data of particular user in the server. This data available till user close

• the browser or session time completes.

• 22. What is CTS and CLS?• =>cls stands for common language specification where as• cts stands for common type system. =>CLS : cls is a standard for .net .

cls is small set of specification to make all languages as a .net• compliant languages. cls make a use of cts and clr. if my languages

(c#,vb.net,j#,vc++) wants to• be compliant language it has to follow cls standard.• =>CTS : Common Type System is also a standard like cls. If two

languages (c# or vb.net or j# or• vc++) wants to communicate with each other, they have to convert into

some common type (i.e.in clr common language runtime). In c# we use int which is converted to Int32 of CLR to

• Communicate with vb.net which uses Integer or vice versa.

• 23. in .NET Compact Framework, can I free memory explicitly without waiting for garbage

• Collector to free the memory?• Yes you can clear the memory using gc.collect method but it is

recommended that u should not• call this coz we don’t know the exact time when the gc will be called

automatic.• 24. What is "Common Type System" (CTS)?• CTS define all of the basic types that can be used in the .NET

Framework and the operations• Performed on those types. All this time we have been talking about

language interoperability,• and .NET Class Framework. None of this is possible without all the

language sharing the same

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• data types. What this means is that an int should mean the same in VB, VC++, C# and all other

• .NET compliant languages. This is achieved through introduction of Common Type System (CTS).

• 25. How do you create a permanent cookie?• By setting the expiry date of the cookie to a later time (like 10 years

later.)• 26. Why is catch(Exception) almost always a bad idea?• 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.

• 27. What is the difference between thread and process?• Thread - is used to execute more than one program at a time.• process - executes single programA thread is a path of execution that

run on CPU, a process is a collection of threads that share• the same virtual memory. A process has at least one thread of

execution, and a thread always• run in a process context.

• 28. How do you turn off cookies for one page in your site?• By setting the Cookie. Discard property false.

• 29. How to get the column count of a report?• SY-LINSZ system variable gives the column count (line size) and SY-

LINCT for line count.• 30. What is Full Trust?• Your code is allowed to do anything in the framework, meaning that all

(.Net) permissions are• granted. The GAC has Full Trust because it’s on the local HD, and that

has Full Trust by default,• you can change that using caspol .

• 31. How can I read .doc document in ASP.Net?• You can read from a text file like this.• private void Button12_Click(object sender, System.EventArgs e)• {• string path="C:Inetpub ew1.txt";• using(StreamReader reader=new StreamReader(path))• {• string line;• while ((line=reader.ReadLine())!=null)• {• Label2.Text+="<br>"+line;• }• }• }• from .doc file try yourself

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• 32. How does the Xml Serializer work? What ACL permissions does a process using it require?

• Xml Serializer requires write permission to the system’s TEMP directory.

• 33. What exactly is being serialized when you perform serialization?

• Serialization is the process of converting an object into stream of bytes. We perform it at the

• time of trans port an object in remoting.

• 34. Briefly explain how server form post-back works ?• Post Back: The process in which a Web page sends data back to the

same page on the server.• View State: View State 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.• View State Maintains the UI State of a Page View State is base64-

encoded. It is not encrypted• but it can be encrypted by setting Enable View Stat MAC="true" &

setting the machine Key• validation type to 3DES. If you want to NOT maintain the View State,

include the directive < %@• Page Enable View State="false" % > at the top of an .aspx page or add

the attribute Enable View• State="false" to any control.

• 35. What is the transport protocol you use to call a Web service SOAP?

• Http is preferred for Soap while tcp for binary i.e. HTTP is used in web services and tcp works

• well in remoting.

• 36. Can you explain what inheritance is and an example of when you might use it?

• The process of deriving a new class from an existing class is called Inheritance. The old class is

• called the base class and the new class is called derived class. The derived class inherits some or

• everything of the base class. In Visual Basic we use the Inherits keyword to inherit one class

• from other.• Ex:• Public Class Base• ---• ---• End Class• Public Class Derived• Inherits Base• ---• End Class

• 37. Differences between Datagrid, Datalist and Repeater?

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• Datagrid has paging while Datalist doesnt.• Datalist has a property called repeat. Direction = vertical/horizontal.

(This is of great help in• designing layouts). This is not there in Datagrid.• A repeater is used when more intimate control over html generation is

required.• When only checkboxes/radiobuttons are repeatedly served then a

checkboxlist or• radiobuttonlist are used as they involve fewer overheads than a

Datagrid.• The Repeater repeats a chunk of HTML you write, it has the least

functionality of the three.• DataList is the next step up from a Repeater; accept you have very little

control over the HTML• that the control renders. DataList is the first of the three controls that

allow you Repeat-• Columns horizontally or vertically. Finally, the DataGrid is• the motherload. However, instead of working on a row-by-row basis,

you’re working on a• column-by-column basis. DataGrid caters to sorting and has basic

paging for your disposal. Again• you have little contro, over the HTML. NOTE: DataList and DataGrid both

render as HTML tables• by default. Out of the 3 controls, I use the Repeater the most due to its

flexibility w/ HTML.• Creating a Pagination scheme isn't that hard, so I rarely if ever use a

DataGrid.• Occasionally I like using a DataList because it allows me to easily list out

my records in rows of• three for instance.

• 38. How different are interface and abstract class in .Net?• Abstract classes can not be instantiated it can have or cannot have

abstract method basically• known as mustinherit as the methods are static in nature• where interfaces are the declaration and r defined where they are called

used for dynamic• methods

• 39. Briefly explain what user controls are and what server controls are and the differences

• between the two.• An ASP.NET control (sometimes called a server control) is a server-side

component that is• shipped with .NET Framework. A server control is a compiled DLL file

and cannot be edited. It• can, however, be manipulated through its public properties at design-

time or runtime. It is• possible to build a custom server control (sometimes called a custom

control or composite

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• control). (We will build these in part 2 of this article.)• In contrast, a user control will consist of previously built server controls

(called constituent• controls when used within a user control). It has an interface that can

be completely edited and• changed. It can be manipulated at design-time and runtime via

properties that you are• responsible for creating. While there will be a multitude of controls for

every possible function• built by third-party vendors for ASP.NET, they will exist in the form of

compiled server controls,• as mentioned above. Custom server controls may be the .NET answer to

ActiveX Web controls.• 40. What is serialization, how it works in .NET?• Serialization is when you persist the state of an object to a storage

medium so an exact copy can• be re-created at a later stage.• Serialization is used to save session state in ASP.NET.• Serialization is to copy objects to the Clipboard in Windows Forms• Serialization is used by remoting to pass objects by value from one

application domain to• another.

• 41. Explain how Viewstate is being formed and how it is stored on client.

• The type of ViewState is System.Web.UI.StateBag, which is a dictionary that stores name/value

• pairs. ViewState is persisted to a string variable by the ASP.NET page framework and sent to the

• client and back as a hidden variable. Upon postback, the page framework parses the input string

• from the hidden variable and populates the ViewState property of each control. If a control uses

• ViewState for property data instead of a private field, that property automatically will be

• persisted across round trips to the client. (If a property is not persisted in ViewState, it is good

• practice to return its default value on postback.)

• 42. What is the root class in .Net ?• Object

• 45. What is Delegation?• A delegate acts like a strongly type function pointer. Delegates can

invoke the methods that• they reference without making explicit calls to those methods.• Delegate is an entity that is entrusted with the task of representation,

assign or passing on• information. In code sense, it means a Delegate is entrusted with a

Method to report

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• information back to it when a certain task (which the Method expects) is accomplished outside

• the Method's class.

• 46. What is Reflection?• It extends the benefits of metadata by allowing developers to inspect

and use it at runtime. For• example, dynamically determine all the classes contained in a given

assembly and invoke their• methods.• Reflection provides objects that encapsulate assemblies, modules, and

types. You can use• reflection to dynamically create an instance of a type, bind the type to

an existing object, or get• the type from an existing object. You can then invoke the type's

methods or access its fields and• properties.• Namespace: System.Reflection

• 47. Describe session handling in a web farm, how does it work and what are the limits ?

• In ASP.NET there are three ways to manage session objects. one support the in-proc mechanism

• and other two's support the out-proc mechanism.o In-Proc (By Default)o SQL-Server (Out-proc) - Using SQL server or any other database

for storing sessions regarding• current logged in user.

o State-Server (Out-Proc) - Using State Server, as one dedicated server for managing sessions.

• State Server will run as service on web server having dotnet installed.

• 48. Can you give an example of when it would be appropriate to use a web service as opposed

• to a non-serviced .NET component?• A web service has the following characteristics:• It communicates using open protocols like HTTP• Processes XML messages framed using SOAP• May be described using WSDL• Can be discovered using UDDI• Any application which is supposed to reach a wide customer base should

be written as a web• service, as opposed to customized applications for specific customers.• For example, services which help in stock trading by providing analysis

of market trends could• best be implemented as a web service. The reasons are• Such a web service would be easily discovered by potential customers

when they need it.• It will require minimal setup on the client machines

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• The updates to the system will be automatically available to all its consumers, without any

• need to deploy the updates on their machines.

• 49. Why The JavaScript Validation Not Run on the Asp.Net?• The Asp.Net Button Is post backed on the server & not yet Submit &

when It goes to the server• its states is lost So if we r using JavaScript in our application so we

always use the Input Button• in the asp Button.

• 50. What are the authentication methods in .NET?• 1.WINDOWS AUTHENTICATION• 2.FORMS AUTHENTICATION• 3.PASSPORT AUTHENTICATION• 4.NONE/CUSTOM AUTHENTICATION• The authentication option for the ASP.NET application is specified by

using the tag in the• Web.config file, as shown below:• other authentication options• WINDOWS AUTHENTICATION Schemes

o Integrated Windows authenticationo Basic and basic with SSL authenticationo Digest authenticationo Client Certificate authentication

• FORMS AUTHENTICATION• You, as a Web application developer, are supposed to develop the Web

page and authenticate• the user by checking the provided user ID and password against some

user database• 3.PASSPORT AUTHENTICATION• A centralized service provided by Microsoft, offers a single logon point

for clients.• Unauthenticated users are redirected to the Passport site• 4 NONE/CUSTOM AUTHENTICATION:• If we don?t want ASP.NET to perform any authentication, we can set the

authentication mode• to ?none?.• The reason behind this decision could be: We don?t want to authenticate

our users, and our• Web site is open for all to use. We want to provide our own custom

authentication.• 51. What is ASP.NET Authentication Providers and IIS Security?• ASP.NET implements authentication using authentication providers,

which are code modules• that verify credentials and implement other security functionality such

as cookie generation.• ASP.NET supports the following three authentication providers:

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• Forms Authentication: Using this provider causes unauthenticated requests to be redirected to a

• specified HTML form using client side redirection. The user can then supply logon credentials,

• and post the form back to the server. If the application authenticates the request (using

• application-specific logic), ASP.NET issues a cookie that• contains the credentials or a key for reacquiring the client identity.

Subsequent requests are• issued with the cookie in the request headers, which means that

subsequent authentications• are unnecessary.• Passport Authentication: This is a centralized authentication service

provided by Microsoft that• offers a single logon facility and membership services for participating

sites. ASP.NET, in• conjunction with the Microsoft? Passport software development kit

(SDK), provides similar• functionality as Forms Authentication to Passport users.

• 52. How many types of assemblies are there , wat are they?• Private, Public/Shared, Satellite. A private assembly is normally used by

a single application, and• is stored in the application's directory. A shared assembly is normally

stored in the global• assembly cache, which is a repository of assemblies maintained by the

.NET runtime. 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.

• 53. What are Attributes?• Attributes are declarative tags in code that insert additional metadata

into an assembly. There• exist two types of attributes in the .NET Framework: Predefined

attributes such as Assembly• Version, which already exist and are accessed through the Runtime

Classes; and custom• attributes, which you write yourself by extending the

• System. Attribute class.

• 54. Can you give an example of when it would be appropriate to use a web service as opposed

• to a non-serviced .NET component?• Webservice:• Appropriate, when exposing the functionalitiss across different Platforms

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• (windows/Linux/Solaris..etc.,) or.NET to J2EE.• .NET Component:• Appropriate, when exposing the functionalities within propritory

O/S(.Net-.Net, or Java-Java• platform)

• 55.How to set a cookie?• HttpCookie myCookie = new HttpCookie("myWebSiteName");• myCookie.Value = "http://www.faqpanel.com/";• myCookie.Expires = DateTime.Now.AddMonths(6);• Response.Cookies.Add(myWebSiteName);

• 56.How to get a cookie?• if (Request.Cookies["myWebSiteName"] != null)• {• string myWebSiteUrl = Request.Cookies["myWebSiteName"].Value;• }

• 57.What is difference between ExecuteReader, ExecuteNonQuery and ExecuteScalar?

• ExecuteReader : Use for accessing data. It provides a forward-only, read-only, connected recordset.

• ExecuteNonQuery : Use for data manipulation, such as Insert, Update, Delete.

• ExecuteScalar : Use for retriving 1 row 1 col. value., i.e. Single value. eg: for retriving aggregate function. It is faster than other ways of retriving a single value from DB.

• 58.What is Strongly Typed Dataset Object?

• Strongly typed Dataset object allows you to create early-bound data retrieval expression.

• Advantage of Strongly Typed dataset• It is faster than late-bound data retrieval expression.• Its column name is shown in intellisense as you type code.

• 59.What is Hashtable in ASP.Net?• The Hashtable object contains items in key/value pairs. The keys are

used as indexes, and very quick searches can be made for values by searching through their keys.

• Items are added to the Hashtable with the Add() method.

• 60.What is Repeater Control in ASP.Net?• The Repeater control is used to display a repeated list of items that are

bound to the control. The Repeater control may be bound to a database table, an XML file, or another list of items.

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• 61.What is DataList Control in ASP.Net?• The DataList control is, like the Repeater control, used to display a

repeated list of items that are bound to the control. However, the DataList control adds a table around the data items by default. The DataList control may be bound to a database table, an XML file, or another list of items.

• 62.What is the "Window Service"?• On Microsoft Windows operating systems, a Windows Service is a long-

running executable that performs specific functions and which is designed not to require user intervention. Windows services can be configured to start when the operating system is booted and run in the background as long as Windows is running, or they can be started manually when required.

• Once a service is installed, it can be managed by launching "Services" from the Windows Control Panel -> Administrative Tools or typing "Services.msc" in the Run command on Start menu. The "Services" management console provides a brief description of the service functions and displays the path to the service executable, its current status, startup type, dependencies and the account under which the service is running. It enables users to:

• Start, stop, pause or restart services.• Specify service parameters.• Change the startup type which includes Automatic, Manual and

Disabled.

• Note: Windows Services is new name for NT Services you used to develop in previous versions of Visual Studio.

• 63.What is Cross Page Posting? How is it done?• By default, ASP.Net submits a form to the same page. In cross-page

posting, the form is submitted to a different page. This is done by setting the PostBackUrl property of the button(that causes postback) to the desired page. In the code-behind of the page to which the form has been posted, use the FindControl method of the PreviousPage property to reference the data of the control in the first page.

• 64.What is typed dataset?• A typed dataset is very much similar to a normal dataset. But the only

difference is that the sehema is already present for the same. Hence any mismatch in the column will generate compile time errors rather

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than runtime error as in the case of normal dataset. Also accessing the column value is much easier than the normal dataset as the column definition will be available in the schema.

• 65.What is System.Web.Mail?• System.Web.Mail (SWM) is the .Net namespace used to send email in

.Net Framework applications. SWM contains three classes:

• MailMessage - used for creating and manipulating the mail message contents.

• MailAttachments - used for creating a mail attachment to be added to the mail message.

• SmtpMail - used for sending email to the relay mail server.

• More information on the System.Web.Mail Namespace can be found on MSDN here:

• 66.Why does the SessionID changes in every request?• This may happen if your application has never stored anything in the

session state. In this case, a new session state (with a new ID) is created in every request, but is never saved because it contains nothing.

• However, there are two exceptions to this same session ID behavior:• If the user has used the same browser instance to request another page

that uses the session state, you will get the same session ID every time.• If the Session_OnStart event is used, ASP.NET will save the session

state even when it is empty.

• 67.In Session_End, do I have a valid HttpSessionState object and HttpContext object?

• You will have the HttpSessionState object available. Just use Session to access it. For HttpContext, it is not available because this event is not associated with any request.

• 68.How come Response.Redirect and Server.Transfer is not working in Session_End?

• Session_End is fired internally by the server, based on an internal timer. And thus there is no HttpRequest associted when that happens. That is why Response.Redirect or Server.Transferdoes not make sense and will not work.

• 69. What does WSDL stand for?• WSDL stands for Web Services Description Language. It is an XML

representation of the web

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• service interface.• There are two types of the operations specified in the WSDL file, as

represented by the• <soap:binding> attribute of the file.• Document oriented operations -- are the ones which contain XML

documents as input and• output• Result oriented operations -- are the ones which contain input

parameters as the input• message and result as the output message

• 70. How can you provide an alternating color scheme in a Repeater control?

• AlternatingItemTemplate Like the ItemTemplate element, but rendered for every otherrow

• (alternating items) in the Repeater control. You can specify a different appearancefor the

• AlternatingItemTemplate element by setting its style properties.

• 71. What are the features of ADO.Net ?• ADO.NET features:• Disconnected Data Architecture• Data cached in Datasets• Data transfer• in XML format• Interaction with the database is done through data commands

• 72. What is an interface and what is an abstract class? Please, expand by examples of using

• both. Explain why?• Abstract classes are closely related to interfaces. They are classes that

cannot be instantiated,• and are frequently either partially implemented, or not at all

implemented. One key difference• between abstract classes and interfaces is that a class may implement

an unlimited number of• interfaces, but may inherit from only one abstract (or any other kind of)

class. A class that is• derived from an abstract class may still implement interfaces. 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.

• 73 .What is reflection?

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• 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).

• 74. What is the difference between a private assembly and a shared assembly?

• 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.

• 75. What is serialization?• 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).

• 76 .Does the .NET Framework have in-built support for serialization?

• 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.

• 77. Why is XmlSerializer so slow?• 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.

• 78. Why do I get errors when I try to serialize a Hashtable?• XmlSerializer will refuse to serialize instances of any class that

implements IDictionary, e.g. Hashtable. SoapFormatter and BinaryFormatter do not have this restriction.

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• 79. XmlSerializer is throwing a generic "There was an error reflecting MyClass" error. How do I find out what the problem is?

• Look at the InnerException property of the exception that is thrown to get a more specific error message.

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• SQl Server 2005

• 1.How many Columns per SELECT statement is possible in SQL Server?

• 4096• 2.What is the difference between a primary key and a unique

key?• Both primary key and unique enforce uniqueness of the column on

which they are defined. But by default primary key creates a clustered index on the column, where are unique key creates a non-clustered index by default. Another major difference is that, primary key does not allow NULLs, but unique key allows one NULL only.

• 3.Write a SQL Query to find first week day of the month?• SELECT DATENAME(dw, DATEADD(dd, - DATEPART(dd, GETDATE()) + 1,

GETDATE())) AS FirstWeekDayofMonth• 4.How to find nth highest salary from Employee table in SQL

Server?SELECT TOP 1 salary FROM (SELECT DISTINCT TOP n salary FROM employee ORDER BY salary DESC) a ORDER BY salary.

• 5.What is the Referential Integrity in SQL Server?• Referential integrity refers to the consistency that must be maintained

between primary and foreign keys, i.e. every foreign key value must have a corresponding primary key value

• 6.What is the row size in SQL Server 2000?• 8060 bytes.• 7.What is the use of DESC in SQL Server Query?• DESC has two purposes. It is used to describe a schema as well as to

retrieve rows from table in descending order.

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• 8.Which function is used in SQL Server to find the largest integer less than or equal to a specific value?

• FLOOR.• 9.Which system table contains information on constraints on all

the tables created in SQL Server?• USER_CONSTRAINTS table.• 10.TRUNCATE TABLE EMP;, DELETE FROM EMP; -What Will the

outputs of the above two commands (Queries) in SQL Server?• Both the statement delete all row from the table EMP, First one can not

be rolled back but second one will be rolled back.• 11.What command is used to create a table by copying the

structure of another table in SQL Server?• CREATE TABLE NEWTABLE AS SELECT command• 12.To copy only the structure, the WHERE clause of the SELECT

command should contain a FALSE statement as in the following.• CREATE TABLE NEWTABLE AS SELECT * FROM EXISTINGTABLE WHERE

1=2;• If the WHERE condition is true, then all the rows or rows satisfying the

condition will be copied to the new table.• 13.What is a constraint in SQL Server?• A constraint is an object that exists only within confines of a table.

Constraints are much like they sound, i.e. - Rules which are enforced on data being entered, and prevents the users from entering invalid data into tables are called constraints. Thus, constraints super control data being entered in tables for permanent storage.

• 14.What is a View in SQL Server?• A View is something like a virtual table in SQL Server. A view is used

just like a table, except that it does not contains any data of its own. Instead, a view is merely a preplanned mapping and representations of the data stored in tables. The plan is stored in the database in the form of query. This query calls for data from some, but not necessarily all, columns to be retrieved from one or more tables.

• 15.The reason why views are created in SQL Server?• When data security is required.• When data redundancy is to be kept to the minimum while maintaining

data security.• 16.What are the Stored procedures (sprocs) in SQL Server?• Stored Procedures are logically grouped set of transect-SQL statement

bundled up into a single unit that perform a specific task. They allow for variables and parameters as well as selection and looping constructs.

• 17.What is difference between function and stored procedure in sql server?

• Stored Procedures may return multiple values, while functions returns only one value at a time.

• 18.Stored Procedures can have input, output parameters for it whereas functions can have only input parameters.

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• Stored Procedure allows select as well as DML statement in it whereas function allows only select statement in it.

• Functions can be called from Stored Procedure whereas Stored Procedures cannot be called from function.

• Exception can be handled by try-catch block in a Stored Procedure whereas try-catch block cannot be used in a function.

• Stored Procedures can not be utilized in a select statement whereas function can be embedded in a select statement.

• Stored Procedures are called independently, using the EXEC command, while functions are called from within another SQL statement.

• 19.What are the benefits of using Stored Procedures in SQL Server?

• OR• Why should we use Stored Procedures?• Precompiled execution. SQL Server compiles each stored procedure

once and then reutilizes the execution plan. This results in tremendous performance boosts when stored procedures are called repeatedly.

• Reduced client/server traffic. If network bandwidth is a concern in your environment, you will be happy to learn that stored procedures can reduce long SQL queries to a single line that is transmitted over the wire.

• Efficient reuse of code and programming abstraction. Stored procedures can be used by multiple users and client programs. If you utilize them in a planned manner, you will find the development cycle takes less time.

• Enhanced security controls. You can grant users permission to execute a stored procedure independently of underlying table permissions.

• 20.Which function is used to find the smallest integer greater than or equal to a specific value in sql server?

• CEILING.

• 21.Which join gives the Cartesian product of two tables in sql server?

• Cross Join.• 22.Explain an outer join?• An outer join includes rows from tables when there are no matching

values in the tables.• 23.What is the difference between group by and order by?• Group by controls the presentation of the rows, order by controls the

presentation of the columns for the results of the SELECT statement.

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• 24.What keyword does an SQL SELECT statement use for a string search?

• The LIKE keyword allows for string searches. The % and _ sign is used as a wildcard.

• 25.What is the DEADLOCK ?• A deadlock is a situation in which two transactions conflict with each

other and the only resolution is to cancel one transaction.• 26.What is a Subquery ?• A Subquery is a normal T-SQL query that is nested inside another query.

They are created using parentheses when you have a SELECT statement that serve as the basis for the either part of the data or the condition in another query.

• Subqueries are generally used to fill one of couple of needs -• Break a query up into a series of a logical steps.• Provide a listing to be the target of a WHERE clause together with [IN|

ESISTS|ANY|ALL].• TO provide a lookup driven by each individual record in a parent query.• Eg.• SELECT SelectList FROM SomeTable WHERE SomeColumn = (SELECT

SingleColumn FROM SomeTable WHERE Condition that results in only one row returned)

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