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Computer Programming ||. Chapter 2: Exception handling. Syllabus. Revision of OOP Exception Handling String manipulation Regular expression Files and Streams Connect applications with DBMS Streams-Based Sockets and Datagrams. Contents. What is an exception error?. Exception handling. - PowerPoint PPT PresentationTRANSCRIPT
Mahmoud Rafeek Alfarra
Computer Programming ||
Chapter 2: Exception handling
SyllabusSyllabus
Revision of OOP Exception Handling String manipulation Regular expression Files and Streams Connect applications with DBMS Streams-Based Sockets and Datagrams
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Contents
Example
Exception Classes in C#
Syntax
Exception handling
What is an exception error?
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Practices
User defined Exception
What is an exception errorWhat is an exception error ? ?
An exception is a problem that arises
during the execution of a program.
A C# exception is a response to an
exceptional situation that arises while a
program is running, such as an attempt to
divide by zero.
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What is an exception errorWhat is an exception error ? ?
Exceptions provide a way to Exceptions provide a way to transfer transfer
controlcontrol from one part of a program to from one part of a program to
another. another.
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Exception handlingException handling
C# exception handling is built upon four keywords:
try: A try block identifies a block of code for which particular exceptions will be activated.
It's followed by one or more catch blocks. catch: A program catches an exception with
an exception handler at the place in a program where you want to handle the
problem. The catch keyword indicates the catching of an exception.
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Exception handlingException handling
C# exception handling is built upon four keywords:
finally: The finally block is used to execute a given set of statements, whether an exception
is thrown or not thrown. For example, if you open a file, it must be closed
whether an exception is raised or not. throw: A program throws an exception when a
problem shows up. This is done using a throw keyword.
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Syntax
Assuming a block will raise and exception, a method catches an exception using a
combination of the try and catch keywords.
You can list down multiple catch statements to catch different type of
exceptions in case your try block raises more than one exception in different
situations.
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Syntaxwww.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra
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Syntax
C# exceptions are represented by classes. The exception classes in C# are mainly
directly or indirectly derived from the System.Exception class.
Some of the exception classes derived from the System.
Exception class are the System.ApplicationException and System.SystemException classes.
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Syntax
The System.ApplicationException class supports exceptions generated by
application programs. So the exceptions defined by the
programmers should derive from this class.
The The System.SystemExceptionSystem.SystemException class is class is the base class for all predefined system the base class for all predefined system
exception. exception.
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Exception Classes in C#www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra
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There are another Exception classes in C#, search about them !!There are another Exception classes in C#, search about them !!
Example 1
1. class Program {
2. public static void division(int num1, int num2)
3. {
4. float result=0.0f;
5. try
6. {
7. result = num1 / num2;
8. }
9. catch (DivideByZeroException e)
10. {
11. Console.WriteLine("Exception Error !! \n divid by zero !!");
12. // Console.WriteLine("Exception caught: {0}", e);
13. }
14. finally
15. {
16. Console.WriteLine("Result: {0} ", result);
17. }
18. }
19. static void Main(string[] args)
20. {
21. division(10,0);
22. Console.ReadLine();
23. } } 13
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Example 2
1. catch (DivideByZeroException ex2)
2. {
3. // …..
4. }
5. catch (FormatException ex1)
6. {
7. //……
8. }14
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Tryex1.MessageTryex1.Message
TryException only
Instead of DivideByZeroException
OrFormatException
TryException only
Instead of DivideByZeroException
OrFormatException
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UseIndexOutOfRangeException
&FormatException
&Exception
UseIndexOutOfRangeException
&FormatException
&Exception
User Defined Exceptionwww.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra
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User Defined Exception
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using System;namespace ExceptionHandling{
class NegativeNumberException:ApplicationException { public NegativeNumberException(string message) // show message }}
if(value<0) throw new NegativeNumberException(" Use Only Positive numbers");
Mahmoud Rafeek Alfarra