using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

​

        // use Regex.Replace to replace the pattern in the input.

        string pattern = @"(?<g1>{NUM})|(?<g2>{\d*NUM})|(?<g3>{NUM\d*})";

        string input = "The quick brown fox {NUM} jumped over {211NUM} the lazy dog {NUM}.  The Quick brown fox {NUM10} jumped over the lazy dog. ";

        Console.WriteLine("*** Simple replace:");

        string output = Regex.Replace(input, pattern, "{CHANGED ${g1}${g2}${g3}}"); 

        Console.WriteLine(output);

        Console.WriteLine();

        Console.WriteLine("*** Replace with MatchEvaluator:");  

        output = Regex.Replace(input, pattern, delegate(Match match)

        {

            if (match.Groups["g1"].Success)

            {

               return "{Group 1}";

            }

            if (match.Groups["g2"].Success)

            {

               return "{Group 2}";

            }

            if (match.Groups["g3"].Success)

            {

               return "{Group 3}";

            }

            //Console.WriteLine(match.Groups.Length);

            return match.Value;

        });

        Console.WriteLine(output);

    }

}