How to get MAC Address of client Machine

NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();

        for (int j = 0; j <= 1; j++)

        {

            PhysicalAddress address = nics[j].GetPhysicalAddress();

            byte[] bytes = address.GetAddressBytes();

            for (int i = 0; i < bytes.Length; i++)

            {

                M = M + bytes.ToString("X2");

                if (i != bytes.Length - 1)

                {

                    M = M + ("-");

                }

            }

        }