Exception Hierarchy 

There are two types of exceptions: exceptions generated by an executing program, and exceptions generated by the common language runtime. In addition, there is a hierarchy of exceptions that can be thrown by either an application or the runtime.

Exception is the base class for exceptions. Several exception classes inherit directly from Exception, including ApplicationException and SystemException. These two classes form the basis for almost all runtime exceptions.

Most exceptions that derive directly from Exception add no functionality to the Exception class. For example, the InvalidCastException Class hierarchy is as follows:

Object    Exception       SystemException          InvalidCastException

The runtime throws the appropriate derived class of SystemException when errors occur. These errors result from failed runtime checks (such as array out-of-bound errors), and can occur during the execution of any method. If you are designing an application that creates new exceptions, you should derive those exceptions from the Exception class. It is not recommended that you catch a SystemException, nor is it good programming practice to throw a SystemException in your application.

The most severe exceptions — those thrown by the runtime or in nonrecoverable conditions — include ExecutionEngineException, StackOverflowException, and OutOfMemoryException.

Interoperation exceptions derive from SystemException and are further extended by ExternalException. For example, COMException is the exception thrown during COM interop operations and derives from ExternalException. Win32Exception and SEHException also derive from ExternalException.

Hierarchy of Runtime Exceptions

The runtime has a base set of exceptions deriving from SystemException that it throws when executing individual instructions. The following table hierarchically lists the standard exceptions provided by the runtime and the conditions under which you should create a derived class.

See Also

Concepts

Exception Class and Properties
Exceptions Overview
Best Practices for Handling Exceptions

Other Resources

Exception Handling Fundamentals
Handling and Throwing Exceptions