Best way to parse command line arguments in C#?

When building console applications that take parameters, you can use the arguments passed to Main(string[] args).

In the past I've simply indexed/looped that array and done a few regular expressions to extract the values. However, when the commands get more complicated, the parsing can get pretty ugly.

So I'm interested in:

• Libraries that you use

• Patterns that you use

Assume the commands always adhere to common standards such as answered here.

I would strongly suggest using NDesk.Options (Documentation) and/or Mono.Options (same API, different namespace). An example from the documentation:

bool show_help = false;
List names = new List ();
int repeat = 1;

var p = new OptionSet () {
    { "n|name=", "the {NAME} of someone to greet.",
       v => names.Add (v) },
    { "r|repeat=", 
       "the number of {TIMES} to repeat the greeting.\n" + 
          "this must be an integer.",
        (int v) => repeat = v },
    { "v", "increase debug message verbosity",
       v => { if (v != null) ++verbosity; } },
    { "h|help",  "show this message and exit", 
       v => show_help = v != null },
};

List extra;
try {
    extra = p.Parse (args);
}
catch (OptionException e) {
    Console.Write ("greet: ");
    Console.WriteLine (e.Message);
    Console.WriteLine ("Try `greet --help' for more information.");
    return;
}

Stack Overflow Q#491595, score: 324