I am looking for a reliable P2P framework or library, preferrably natively written in C#, but can also work with something C# can interface with. Have you came across or have worked with a solid one?
Take a look at this link:
Brunet: a remarkably great P2P library
Brunet is a Free Software (GPL licensed) library for P2P networking written in C# and developed using Mono, but it also runs on Microsoft’s .Net platform.