get the client mac address

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Runtime.InteropServices;

namespace AspDoNet.Manage.CommonMethod
{
    public partial class FunctionList : System.Web.UI.Page
    {
        [DllImport("Iphlpapi.dll")]

        private static extern int SendARP(Int32 dest, Int32 host, ref Int64 mac, ref Int32 length);
        [DllImport("Ws2_32.dll")]
        private static extern Int32 inet_addr(string ip);
        protected void Page_Load(object sender, EventArgs e)
        {
            try
            {
                string userip = Request.UserHostAddress;
                string strClientIP = Request.UserHostAddress.ToString().Trim();
                Int32 ldest = inet_addr(strClientIP); 
                Int32 lhost = inet_addr("");   
                Int64 macinfo = new Int64();
                Int32 len = 6;
                int res = SendARP(ldest, 0, ref macinfo, ref len);
                string mac_src = macinfo.ToString("X");
                if (mac_src == "0")
                {
                    if (userip == "127.0.0.1")
                        Response.Write("visited Localhost!");
                    else
                        Response.Write("the IP from" + userip + "" + "<br>");
                    return;
                }

                while (mac_src.Length < 12)
                {
                    mac_src = mac_src.Insert(0, "0");
                }

                string mac_dest = "";

                for (int i = 0; i < 11; i++)
                {
                    if (0 == (i % 2))
                    {
                        if (i == 10)
                        {
                            mac_dest = mac_dest.Insert(0, mac_src.Substring(i, 2));
                        }
                        else
                        {
                            mac_dest = "-" + mac_dest.Insert(0, mac_src.Substring(i, 2));
                        }
                    }
                }

                Response.Write("welcome" + userip + "<br>" + ",the mac address is" + mac_dest + "."

                 + "<br>");
            }
            catch (Exception err)
            {
                Response.Write(err.Message);
            }
        }
   


    }
}