List of Free code ANTLR
ANTLR C# grammar
This project will generate a C# 4.0 parser using ANTLR v3.2. Then you can add your own logic to do what you want.
It generates CSharp target and has a reasonably small amount of code for the preprocessor in the lexar.
Wiki .NET Parser, Open Source project powered by ANTLR. Syntax defined in 3(4) files Lexer, Grammar, AST Parser.