Exceptions - Illustrated C# 2005 - page 272

The catch Clauses Section
The catch clauses section can contain multiple catch clauses. Figure 11-4 shows a summary
of the catch clauses section.

Figure 11-4. Structure of the catch clauses section of a try statement

When an exception is raised, the list of catch clauses is searched in order, and the first
catch clause that matches the type of the exception object is executed. Because of this, there
are two important rules in ordering the catch clauses. They are the following:

￿The spec ic catch clauses must be ordered with the most specific exception types first,
progressing to the most general. For example, if you declare an exception class derived
from NullReferenceException , the catch clause for your derived exception type should
be listed before the catch clause for NullReferenceException .

￿ If there is a general catch clause, it must be the last clause—after all specific catch

clauses.