Pro C# 2010 and the .NET 4 Platform, Fifth Edition

7.6. Application-Level Exceptions (System.ApplicationException)

Given that all .NET exceptions are class types, you are free to create your own application-specific exceptions. However, due to the fact that the System.SystemException base class represents exceptions thrown from the CLR, you may naturally assume that you should derive your custom exceptions from the System.Exception type. You could do this, but you could instead derive from the System.ApplicationException class:

public class ApplicationException : Exception
{
  //  Various constructors.
}

Like SystemException, ApplicationException does not define any additional members beyond a set of constructors. Functionally, the only purpose of System.ApplicationException is to identify the ...