using System;
using System.Windows.Forms;
using System.Net;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                IPHostEntry hostname = Dns.GetHostByName(textBox1.Text );
                IPAddress[] ip = hostname.AddressList;
                textBox2.Text  = ip[0].ToString(); 
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }
    }
}