using System; using System.Text; using System.Text.RegularExpressions; public class EntryPoint { static void Main( string[] args ) { // Create regex to search for IP address pattern. string pattern = @"(?<part1>[01]?dd?|2[0-4]d|25[0-5])." + @"(?<part2>[01]?dd?|2[0-4]d|25[0-5])." + @"(?<part3>[01]?dd?|2[0-4]d|25[0-5])." + @"(?<part4>[01]?dd?|2[0-4]d|25[0-5])"; Regex regex = new Regex( pattern ); Match match = regex.Match( "192.168.169.1" ); MatchEvaluator eval = new MatchEvaluator(EntryPoint.IPReverse ); Console.WriteLine( regex.Replace("192.168.169.1", eval) ); } static string IPReverse( Match match ) { Console.WriteLine( match.Groups["part4"] + "." ); Console.WriteLine( match.Groups["part3"] + "." ); Console.WriteLine( match.Groups["part2"] + "." ); Console.WriteLine( match.Groups["part1"] ); return ""; } }