csharp_regex.cs

// Dealing with named grouping in regular expressions in .net
using System;
using System.Text.RegularExpressions;
using System.Collections;

public class RegexEg1
{
  static public void Main ()
  {
    string[] words = new string[] {
                                  "Tom,32,Denver,tom1",
                                  "Jill,27,New York,jill",
                                  "Bill,49,12345,bill1",
                                  "John,22,Phoenix,john",
                                  "Tom,73,Albany,tom2",
                                };

    string pattern = @"^(?<firstname>[A-Za-z]+),(?<age>\d+),(?<city>[a-zA-Z]+( [a-zA-Z]+)?),(?<userid>\w+)$";

    Regex regex = new Regex(pattern);
    foreach (string word in words)
    {

      Boolean is_match = false;
      foreach (Match m in regex.Matches(word))
      {
        is_match = true;
        Console.WriteLine("matched: " + word + " (" +
                "firstname=" + m.Groups["firstname"].Value + ", " +
                "age="       + m.Groups["age"].Value + ", " +
                "city="      + m.Groups["city"].Value + ", " +
                "userid="    + m.Groups["userid"].Value +
              ")" );
      }
      if (!is_match)
      {
        Console.WriteLine("UNMATCHED: " + word);
      }

    }

  }

}


Output:
matched: Tom,32,Denver,tom1 (firstname=Tom, age=32, city=Denver, userid=tom1)
matched: Jill,27,New York,jill (firstname=Jill, age=27, city=New York, userid=jill)
UNMATCHED: Bill,49,12345,bill1
matched: John,22,Phoenix,john (firstname=John, age=22, city=Phoenix, userid=john)
matched: Tom,73,Albany,tom2 (firstname=Tom, age=73, city=Albany, userid=tom2)