CSLua is a pure C# library for interfacing to the Lua 5.1 Windows DLL. It supports the core Lua API and includes a C# class wrapper for binding C# objects from Lua script.
I have posted a page for CSLua at the link below. This includes the full Visual Studio 2008 (I use express edition, but any version should work) test solution and library project. It can be used as stand-alone source or build the managed DLL from the project.