Development Class C#

using System;
using System.Text.RegularExpressions;
public class EntryPoint
{
    static void Main( string[] args ) {
        // Create regex to search for IP address pattern.
        string pattern = @"(?[01]?\d\d?|2[0-4]\d|25[0-5])\." +
                         @"(?[01]?\d\d?|2[0-4]\d|25[0-5])\." +
                         @"(?[01]?\d\d?|2[0-4]\d|25[0-5])\." +
                         @"(?[01]?\d\d?|2[0-4]\d|25[0-5])";
        Regex regex = new Regex( pattern );
        Match match = regex.Match( "192.168.169.1" );
        while( match.Success ) {
            Console.WriteLine( "IP Address found at {0} with " +
                               "value of {1}",
                               match.Index,
                               match.Value );
            Console.WriteLine( "Groups are:" );
            Console.WriteLine( "\tPart 1: {0}",
                               match.Groups["part1"] );
            Console.WriteLine( "\tPart 2: {0}",
                               match.Groups["part2"] );
            Console.WriteLine( "\tPart 3: {0}",
                               match.Groups["part3"] );
            Console.WriteLine( "\tPart 4: {0}",
                               match.Groups["part4"] );
            match = match.NextMatch();
        }
        
    }
}