MatchesDemo.zip

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Windows.Forms;

 namespace MatchesDemo
 {
     public partial class IPValidate : Form
     {
         public IPValidate()
         {
             InitializeComponent();
         }

         private void btnValidate_Click(object sender, EventArgs e)
         {
             // MessageBox.Show(mtxtIPAddress.Text);

             // create a regex object
             Regex checkIP = new Regex (@"\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b");

             // create match
             Match matchIP = checkIP.Match(mtxtIPAddress.Text);

             if (checkIP.IsMatch(mtxtIPAddress.Text))
             {
                 mtxtIPAddress.ForeColor = Color.Green;
             }
             else
                 mtxtIPAddress.ForeColor = Color.Red;
         }
     }
 }