I haven't written much LISP, though I'm familiar with C#.
C# isn't a scripting language, in my understanding it interacts with CAD in a different manner than LISP. You may be able to use some of the logic from your LISP code, but as far as I know there is to tool for LISP/.NET translation.
As others have said, if you're migrating to C# you should get familiar with C#/.NET first, then start applying it to AutoCAD.