How to find client's MAC Address in Asp.Net and C#.net

For Web Application

using System.Runtime.InteropServices;

[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);
        }
    }
-----------------------------------------------------------------------------------------------------------------------


For Window Application

public string GetMACAddress()
{
    NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
    String sMacAddress = string.Empty;
    foreach (NetworkInterface adapter in nics)
    {
        if (sMacAddress == String.Empty)// only return MAC Address from first card 
        {
            IPInterfaceProperties properties = adapter.GetIPProperties();
            sMacAddress = adapter.GetPhysicalAddress().ToString();
        }
    } return sMacAddress;

}