Thanks for this, its clear and explained well, the example works. I am guessing from my experimentation though that there are some serious limitations to this method. I have a dll, that is comprised of multiple classes, and uses Reflection and and System.Diagnostics to gather information from the calling program, it also uses the IDisposable interface. Needless to say I could not quite get it to work with perl...yet at least. If you have any examples of more comples C# dll's I would appreciate the information. Thanks again great post :-)