asp.net如何获取客户端网卡mac地址?

asp.net如何获取客户端网卡mac地址?
下面的这种只能取到服务器端的!
            ManagementClass mc = new ManagementClass("Win32_NetworkAdapterConfiguration");
            ManagementObjectCollection moc2 = mc.GetInstances();
            foreach (ManagementObject mo in moc2)
            {
                if ((bool)mo["IPEnabled"] == true)
                    v_localUnique = mo["MacAddress"].ToString();
                mo.Dispose();
            }下面这种也不行
            string mac="";
            Process process=new Process();
            process.StartInfo.FileName="nbtstat";
            string ip = Request.UserHostAddress.ToString();
            process.StartInfo.Arguments = "-a " + ip;
            process.StartInfo.UseShellExecute=false;
            process.StartInfo.CreateNoWindow=true;
            process.StartInfo.RedirectStandardOutput=true;
            process.Start();
            string output=process.StandardOutput.ReadToEnd();
            int length=output.IndexOf("MAC Address =");
            if(length>0)
            {
                mac=output.Substring(length+14,17);
            }             
不知是我用错了,还是其它的什么问题!望大家帮帮我!