Active document support/alternative in .NET

I want to make a .NET application in C# that can act as an active document server. To my disappointment I can't find any support for it.
Has anyone implemented the interfaces that are necessary to support it in .NET?

What would be the typical alternative to active document in .NET?

I'm bumping this post instead of starting a new thread.

Our company MUST create an Active Document Server because another application launches ours and that is the technology they use -- and they won't be changing for at least 5 years (if ever).

To make matters worse, objects and code developed by another department which we need to incorporate is all done using .NET (C#).

So, somehow we need to create a managed (/CLR) Active Document Server using MFC that is launched by an unmanaged Active Document Container not developed by us, just so we can run managed .NET (C#) code developed by another department.

ActiveX Document support was suspended from .NET during beta but couldn't Microsoft at least present a solution for those of us left hanging?