asp.net 获得客户端 mac 地址

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 WebTestMac
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string str = GetCustomerMac(GetClientIP());
            Response.Write(str);
        }
        [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);

        private string GetClientIP()
        {
            string result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (null == result || result == String.Empty)
            {
                result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }

            if (null == result || result == String.Empty)
            {
                result = HttpContext.Current.Request.UserHostAddress;
            }
            return result;
        }
        /// <summary>   
        /// 获取Mac地址信息   
        /// </summary>   
        /// <param name="IP"></param>   
        /// <returns></returns>   
        public static string GetCustomerMac(string IP)
        {
            Int32 ldest = inet_addr(IP);
            Int64 macinfo = new Int64();
            Int32 len = 6;
            int res = SendARP(ldest, 0, ref macinfo, ref len);
            string mac_src = macinfo.ToString("X");

            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));
                    }
                }
            }

            return mac_dest;
        }

    }
}