To create a custom exception class, you should define a type. When designing custom exception classes, you should derive your class from System.Exception and not from ApplicationException.

However, throwing exceptions is costly in terms of performance, so we should avoid them in our code. This article discusses a few strategies we can use to avoid exceptions in C#.

If you really want to take full control of the exceptions you pass to your clients, you can write your own Exception class. Here's how to do that, complete with support for additional properties.