Throwing (or raising) an exception halts execution of your program at that point, and execution proceeds in the most immediately available catch block (exception handler).

A bug is a programming mistake that should be fixed before the program is released. An exception, however, is the result of a predictable but unpreventable problem that arises during runtime (for example, running out of disk space).

When a program encounters a problem that it cannot solve or work around, it may throw an exception to halt execution and allow the exception handler to fix or work around the problem.

All exceptions used in C# derive from System.Exception, and all exceptions in your program should derive from System.Exception.

You can throw an exception yourself using the throw keyword.

It is good programming practice to enclose code that has a high risk of throwing an exception within a try block and to provide an exception handler (a catch block) and perhaps a finally block.

The catch block follows the try block and contains the code used to handle the exception.

If an exception was not raised within a try block, or there is no catch block, the stack is unwound until a catch block is found. If no catch block is ever found, the built-in exception handler is invoked, which terminates your program with an error message.

You can create dedicated catch statements to catch specific types of exceptions taking advantage of the inheritance hierarchy of exceptions.

Any action that must be taken whether or not an exception is raised (such as closing a file) should be enclosed in a finally block.

An exception object can contain information about the circumstances that cause the exception to be raised. Typically, exception objects contain at least a text message explaining the exception, in the Message property.

You can define your own exception class, derived from System.Exception, if you need to provide more specific information about your exception.