One pattern I’ve started running into is developers explicitly throwing a NullReferenceException when validating the “this” parameter of an extension method. public static void ForEach<T>( this IEnumerable <T> enumerable, Action <T> action) { if ( null == enumerable) { throw...

One of the more frequent questions I answer on StackOverflow is a variation of the following.  I’m doing XXX with a file, how can I know if the file exists? The variations include verify no one else has the file open, if the file is in use, the file is not writable, etc ….  The answer to all...

In responding to a recent blog post , one of the readers, Jeremy Gray, noted that I was using a NotImplementedException where I should have been using a NotSupportedException .  At first I did not agree.  There was a method on an interface which my underlying object could not implement therefore...

Answer: When you're the one who threw it.  Starting with the CLR version 2.0, the policy for handling a StackOverflowException was changed.  User code can no longer handle the exception[1].  Instead the CLR will simply terminate the process.  This is not 100% true though.  User...

I think the best answer is: rarely.   It's really hard to go straight to a justification here though.  I find that answering a different question will eventually shed led on when to create a new exception. "What are the benefits of creating a new/custom exception?" The answers...