using System;

using System.Net;

using System.Net.Sockets;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        checkIP ip = new checkIP();

        string ipaddr;

        for (int i = 0; i < 10; i++)

        {

            Console.WriteLine("please enter ip address");

            ipaddr = Console.ReadLine();

            if (ip.IsIpV4AddressValid(ipaddr))

            {

                Console.WriteLine("Ip is valid");

            }

            else

            {

                Console.WriteLine("Ip is not valid");

            }

        }       

    }

}

​

public class checkIP

{

    private static readonly Regex validIpV4AddressRegex = new Regex(@"^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$", RegexOptions.IgnoreCase);

    /// <summary>

    /// Validates an IPv4 address.

    /// </summary>

    /// <param name="address"></param>

    /// <returns></returns>

    public bool IsIpV4AddressValid(string address)

    {

        if (!string.IsNullOrWhiteSpace(address))

        {

            return validIpV4AddressRegex.IsMatch(address.Trim());

        }

​

        return false;

    }

​

    /// <summary>

    /// Validates an IPv6 address.

    /// </summary>

    /// <param name="address"></param>

    /// <returns></returns>

    public static bool IsIpV6AddressValid(string address)

    {

        if (!string.IsNullOrWhiteSpace(address))

        {

            IPAddress ip;

            if (IPAddress.TryParse(address, out ip))

            {

                return ip.AddressFamily == AddressFamily.InterNetworkV6;

            }

        }

        return false;

    }   

}