using System;
using System.Text;
using System.Text.RegularExpressions;
public class MainClass
{
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( "192.168.123.1" );
string replace = @"${part4}.${part3}.${part2}.${part1}" +
@" (the reverse of $&)";
Console.WriteLine( regex.Replace("192.168.123.1", replace) );
}
}
1.123.168.192 (the reverse of 192.168.123.1)