Did you actually read my entire comment, or did you just see "C#" and post a knee-jerk reaction? If you extract code from C# to C, you don't need a GC or any of the .NET class libraries -- you'd just have a standalone C file to use like any other.
Perhaps another way of saying this is that you will always need a runtime. And if you reimplement the portions of the runtime that you need in C, you've essentially re-implemented .NET.
