Exceptions - Illustrated C# 2005 - page 270

The catch Clause
The catch clause handles exceptions. There are three forms of the catch clause, allowing differ-
ent levels of processing. The forms are shown in Figure 11-3.
Figure 11-3. The three forms of the catch clause
The general catch clause can accept any exception, but cannot determine the type of
exception that caused it. This allows general processing and cleanup for whatever exception
might occur.
The specific catch clause form takes the name of an exception class as a parameter. It
matches exceptions of the specified class or exception classes derived from it.
The specific catch clause with ID form gives you the most information about the exception.
It matches exceptions of the specified class, or exception classes derived from it. It also gives
you an exception instance ID, called the exception variable , which is a reference to the excep-
tion object created by the CLR. You can access the exception variable's properties within the
block of the catch clause to get specific information about the exception raised.
For example, the following code handles exceptions of type IndexOutOfRangeException .
When one occurs, a reference to the actual exception object is passed into the code with
parameter name e . The three WriteLine statements each read a string field from the excep-
tion object.
Exception type Exception variable
↓ ↓
catch ( IndexOutOfRangeException e )
{ Accessing the exception variable
↓
Console.WriteLine( "Message: {0}", e.Message );
Console.WriteLine( "Source: {0}", e.Source );
Console.WriteLine( "Stack: {0}", e.StackTrace );