I have an old MFC app written in Visual Studio 6. This will at some point be rewritten in C# .NET. However, before then I have to write a couple of new Windows services for the existing application. The others were written in ATL. What I would prefer to do is write these new services in C# .NET so that when the rest of the application is rewritten, these don't need to be.

Is it going to be possible to call the interfaces on the libraries hosted in a .NET windows service from the old application? If so, could you please explain how.