Let me elaborate, before someone is thundering down on me with "Never reuse a COM interface!!!"
We implemented an COM interface on a program which is discontinued. We now actually buy a similar piece of software from a third party (so I can't change that!)
The COM interface is still used by many (third party) programs. Now I have to integrate the new piece of software with these programs (which I can't change because they are third party).
So I think I need a proxy: This proxy will reuse the COM interface so none of the third party programs will be able to tell they're not talking to the discontinued software. Inside the COM object, I'll 'translate' the commands and forward them to the new piece of software.
I'm using C# to build my proxy and I've used the tlbimp.exe to generate a DLL from the type library of the old program.
I'm referencing this generated DLL in my COM project where I provide a implementation for the given interface. Next, I register the output DLL from my project and use a old client to call the proxy.
It returns the error: Unable to cast object of type 'Lib.ApiClass' to type 'Lib.ApiClass'.
Why is that? Should I use a different approach?