This goes a lot further than the basics, but the basics are there.

http://msdn.microsoft.com/en-us/library/ms947579.aspx

Or the updated article at http://craigberntson.com/docs/complus.pdf

>I have seen it recommended to base DLL on session class so that it has a separate data session. It seems from what you and Craig are saying that a DLL will always have a separate data session - in which case why is the session class recommended over say the Custom class?
>
>Sorry for the rather basic questions - I have not created COM servers in VFP before.
>
>Barry