using System;

using System.Text.RegularExpressions;               

public class Program

{

    public static void Main()

    {

        string input="Hallo abc23 abc24";

        string pattern = @"abc(\d+)";

​

   Regex rgx = new Regex(pattern);

   MatchCollection matches = rgx.Matches(input);

   if (matches.Count > 0)

   {

      Console.WriteLine("{0} ({1} matches):", input, matches.Count);

       foreach (Match match in matches){

          GroupCollection groups = match.Groups;

           Console.WriteLine("   " + groups[1]);

       }

   }

​

​

    }

}