Programming C#, Third Edition

Exception Objects

So far you’ve been using the exception as a sentinel—that is, the presence of the exception signals the error—but you haven’t touched or examined the Exception object itself. The System.Exception object provides a number of useful methods and properties. The Message property provides information about the exception, such as why it was thrown. The Message property is read-only; the code throwing the exception can set the Message property as an argument to the exception constructor.

The HelpLink property provides a link to the help file associated with the exception. This property is read/write.

Tip

VB6 programmers take note: In C#, you need to be careful when declaring and instantiating object variables on the same line of code. If there is a possibility that an error could be thrown in the constructor method, then you might be temped to put the variable declaration and instantiation inside the try block. But if you do that, the variable will only be scoped within the try block and it can’t be referenced within the catch or finally blocks. The best approach is to declare the object variable before the try block and instantiate it within the try block.

The StackTrace property is read-only and is set by the runtime. In Example 11-6, the Exception.HelpLink property is set and retrieved to provide information to the user about the DivideByZeroException. The StackTrace property of the exception is used to provide a stack trace for the error statement. A stack trace ...