1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor
The first 3D game engine built in C# for .NET, predecessor to the Visual3D Game Engine (https://www.poweraccess.net/visual3d-game-engine), an All-in-One Game Development Tool for Next-Gen 3D Games, MMOs, Simulations and Virtual Worlds powered by Microsoft XNA.
NHost is a universal server for DotNet objects. You create your assemblies with business objects and then use NHost to publish them. It is written in C# and works on .NET, Portable.NET and Mono on Linux and Windows.