C# 5.0 Programmer's Reference

222 ❘ CHAPTER 9 Error Handling
described in the previous sections, if one exists. If there is no UnhandledException event handler, the
program crashes.
If you include a catch statement with no exception type, that block matches any exception. If
the raised exception doesn’t match any of the previous exception types, the program executes the
finalExceptionStatements block of code. Note that the statement catch (Exception ex) also
matches all exceptions, so it’s just as good as catch by itself. It also gives you easy access to the
exception object’s properties and methods.
You can figure out what exception classes to use in catch statements in several ways. First, you can
spend a lot of time digging through the online help. An easier method is to let the program crash
and then look at the error message it produces.
Figure 9-4 shows the error message a program throws when it tries to use the Integer.Parse
method to convert the non-numeric string Hello into an integer. The first line in the dialog makes
it obvious that the program should catch FormatException.
Figure 9-4: When a program crashes, the message it
generates tells you the type of exception it threw.
Another way to decide what types of exceptions to catch is to place a final generic catch (Exception
ex) statement at the end of the catch list. Place code inside that catch block to display the exception’s
type name, as shown in the following code.
try
{
...
}
... Catch blocks ...
catch (Exception ex)
{
MessageBox.Show("Unexpected exception " + ex.GetType().Name);
}
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