Nester is a .NET port of Jester slightly adjusted for C# -
see http://nester.sourceforge.net/
Now Jester (version 1.30) can be told to ignore parts of source files, e.g. comments, much better than before.
See the hits and tips page http://jester.sf.net/hintsAndTips.html for instructions on making Jester use Ant or Jikes to compile the source that it has modified - Ant is good for source with more complicated build requirements, Jikes is much faster than javac.