I've been reading all day and I can't find it....

Question

Hello people, I'm trying to figured out a way to migrate an API shell from VB6 to C# and make it seamless to the rest of the applications...Meaning that I wish my C# DLL to be Binary Compatible with the VB6 DLL already in place...The functions will be the same put we will be adding to the API and I don't wish to change the client applications using said API... Any input would be nice, Thanks, Fred-O