Given a regex pattern, I\'m trying to find a string that matches it. Similar to how Django reverses them, but in C#. Are there any pre-made C# libraries that do this?
"Are there any pre-made C# libraries that do this?"
NO
(I expect this will be accepted as the answer momentarily)
see for example Using Regex to generate Strings rather than match them
also you can take a look at http://en.wikipedia.org/wiki/Deterministic_finite-state_machine especially at "Accept and Generate modes" section.
as others noted you will need to create a DFA from your regular expression and then generate your strings using this DFA.
to convert your regular expression to DFA, generate NFA first (see for example http://lambda.uta.edu/cse5317/spring01/notes/node9.html) and then convert NFA to DFA.
the easiest way i see is to use a parser generator program for that. i do not think django does this.
hope this helps.