C# 4 and .NET 4

15
errors and exceptions
WhaT ’ s in This ChaPTer
➤
➤
➤
Looking at the exception classes
U s in g try...catch...finally to capture exceptions
Creating user - defi ned exceptions
Errors happen, and they are not always caused by the person who coded the application. Sometimes
your application will generate an error because of an action that was initiated by the end user of your
application or it might be simply due to the environmental context in which your code is running. In
any case, you should anticipate errors occurring in your applications and code accordingly.
The .NET Framework has enhanced the ways in which you deal with errors. C# ’ s mechanism for
handling error conditions allows you to provide custom handling for each type of error condition as
well as to separate the code that identifi es errors from the code that handles them.
By the end of this chapter, you will have a good grasp on advanced exception handling in your C#
applications.
No matter how good your coding is, your programs should have the ability to handle any possible
errors that may occur. For example, in the middle of some complex processing of your code, you may
discover that it doesn ’ t have permission to read a fi le, or, while it is sending network requests, the
network may go down. In such exceptional situations, it is not enough for a method to simply return
an appropriate error code — there might be 15 or 20 nested method calls, so what you really want
the program to do is jump back up through all those 15 or 20 calls to exit the task completely and
take the appropriate counteractions. The C# language has very good facilities to handle this kind of
situation, through the mechanism known as exception handling.
If you are a Java or C++ developer you are familiar with the principle of exceptions
because these languages handle errors in a similar way to C#. Developers using C++
are sometimes wary of exceptions because of possible C++ performance implications,
but this is not the case in C#. Using exceptions in C# code in general does not adversely
affect performance. Visual Basic developers will fi nd that working with exceptions in C#
is very similar to using exceptions in Visual Basic (except for the syntax differences).
www.it-ebooks.info