What are some best practices for creating my own custom exception?

In a follow-up to a previous question regarding exceptions, what are best practices for creating a custom exception in .NET?

More specifically should you inherit from System.Exception, System.ApplicationException or some other base exception?

From stackoverflow mattruma

• I think the single most important thing to remember when dealing with exceptions at any level (making custom, throwing, catching) is that exceptions are only for exceptional conditions.

  From Thomas Owens

• Inherit from System.Exception. System.ApplicationException is useless and the design guidelines say "Do not throw or derive from System.ApplicationException."

  See http://blogs.msdn.com/kcwalina/archive/2006/06/23/644822.aspx

  From Mark Cidade

• See this question: http://stackoverflow.com/questions/52753/derive-from-exception-or-applicationexception-in-net

  From rp

• The base exception from where all other exceptions inherit from is System.Exception, and that is what you should inherit, unless of course you have a use for things like, say, default messages of a more specific exception.

  From Jon Limjap

• There is a code snippet for it. Use that. Plus, check your code analysis afterwards; the snippet leaves out one of the constructors you should implement.

  From Will

• In the C# IDE, type 'exception' and hit TAB. This will expand to get you started in writing a new exception type. There are comments withs links to some discussion of exception practices.

  Personally, I'm a big fan of creating lots of small classes, at that extends to exception types. For example, in writing the Foo class, I can choose between:

  1. throw new Exception("Bar happened in Foo");
  2. throw new FooException("Bar happened");
  3. throw new FooBarException();

  where

  class FooException : Exception 
  {
      public FooException(string message) ... 
  }
  

  and

  class FooBarException : FooException 
  {
      public FooBarException() 
          : base ("Bar happened") 
      {
      }
  }
  

  I prefer the 3rd option, because I see it as being an OO solution.

  From Jay Bazuzi