There's serveral different ways of exposing your objects through COM. None of them are what I would call ".NET easy". Which method is best for you depends on your skill level, COM knowledge, Win32 API experience, ... Google for "C# out of process COM server" or "C# DCOM Server" and you'll get a ton of articles, opinions, pitfalls, and examples, but little in the way of documentation.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak