Exception Types
There are a number of exception classes provided by C#, all of which inherit
from the System.Exception class. Following are some common exception classes.
|
Exception Class
|
Cause
|
SystemException
|
A failed run-time check;used as a base class for other.
|
AccessException
|
Failure to access a type member, such as a method
or field. |
ArgumentException
|
An argument to a method was invalid. |
ArgumentNullException
|
A null argument was passed to a method that doesn't
accept it. |
ArgumentOutOfRangeException
|
Argument value is out of range. |
ArithmeticException
|
Arithmetic over - or underflow has occurred. |
ArrayTypeMismatchException
|
Attempt to store the wrong type of object in an array.
|
BadImageFormatException
|
Image is in the wrong format. |
CoreException
|
Base class for exceptions thrown by the runtime. |
DivideByZeroException
|
An attempt was made to divide by zero. |
FormatException
|
The format of an argument is wrong. |
IndexOutOfRangeException
|
An array index is out of bounds. |
InvalidCastExpression
|
An attempt was made to cast to an invalid class. |
InvalidOperationException
|
A method was called at an invalid time. |
MissingMemberException
|
An invalid version of a DLL was accessed. |
NotFiniteNumberException
|
A number is not valid. |
NotSupportedException
|
Indicates sthat a method is not implemented by a class.
|
NullReferenceException
|
Attempt to use an unassigned reference. |
OutOfMemoryException
|
Not enough memory to continue execution. |
StackOverflowException
|
A stack has overflown. |
The finally block is used to do all the clean up code. It does not support
the error message, but all the code contained in the finally block is executed
after the exception is raised. We can use this block along with try-catch and
only with catch too.
The finally block is executed even if the error is raised. Control is always
passed to the finally block regardless of how the try blocks exits.
This is shown in the following example:
int a, b = 0 ;
Console.WriteLine( "My program starts" ) ;
try
{
a = 10 / b;
}
catch ( InvalidOperationException e )
{
Console.WriteLine ( e ) ;
}
catch ( DivideByZeroException e)
{
Console.WriteLine ( e ) ;
}
finally
{
Console.WriteLine ( "finally" ) ;
}
Console.WriteLine ( "Remaining program" ) ;
The output here is:
My program starts
System.DivideByZeroException: Attempted to divide by zero.
at ConsoleApplication4.Class1.Main(String[] args) in d:\programs\consoleapplication4\class1.cs:line
51
finally
Remaining program
But then what's the difference? We could have written
Console.WriteLine ("finally");
after the catch block, and not write the finally block at all. Writing finally
did not make much of a difference. Anyway the code written after catch gets executed.
The answer to this is not clear in this program. It will be clear when we see
the try-finally and the throw statement.