Please see the framework 4.0 advice at
In particular you should note the statement "If you are designing an application that needs to create its own exceptions, you are advised to derive custom exceptions from the
Exception class. It was originally thought that custom exceptions should derive from the
ApplicationException class; however in practice this has not been found to add significant value. "
Should StyleCop add a rule to depreciate the use of ApplicationException or is this more properly in realm of the FXCOP team?