I worked off version 0.28 of the C# Language Specification (of 5/7/2001). I've tested the scanner/parser on about 3,000 C# programs, and it seems to be working ok. In all cases, when resolving conflicts in the grammar I've gone for the "most general" approach - thus, the parser should accept all valid programs, but will also allow some invalid ones as well.

There are a few points you should note:

• There's no preprocessor - I just ignore all lines starting with a "#". This could mean that some technically correct programs get rejected, but I think this is reasonably unlikely.
• The bison grammar has one s/r conflict - the dangling else. It also has one r/r conflict related to the ambiguity between types and expressions, but I don't think this is a problem.
• It's very basic - there's no fancy error handling or anything nice like that
• As regards the disambiguation - you should read chapter 19 of the Java Language Specification, as the comments they make are relevant to C# too.
• I had lots of problems trying to disambiguate rank specifiers from array element access. In the end, I just make rank specifiers into a token, rather than suffer any more rewriting of the grammar rules. This could cause problems if there's something unexpected (like a comment) in the middle of a rank specifier.
• The lexical specification talks about UNICODE characters - I haven't done anything about this.

You might also like to check out the mono C# compiler. This has a parser for a bison-like tool (that generates C#), along with lots of C# code. (I'm not connected with the mono project in any way).

I presented a paper about the parser's design as Applying Software Engineering Techniques to Parser Design at the Conference of the South African Institute of Computer Scientists and Information Technologists, in Port Elizabeth, South Africa, September 16-18 2002.

If you find any bugs in this, or thing there's something else I should mention here, let me know.

Download

To make an application out of this, here's a minimal program main.c, and a Makefile.

Or you can get all of these files as a single .zip file: csharp.zip.

I made these using flex version 2.5.4 and bison version 1.28, but I don't think there's anything too special in there. I do use exclusive start conditions as well as start-condition stacks in the lexer - these may not be available in all flex/lex variants.