C# Get Clinent MacAddress

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Management;
using System.Net.NetworkInformation;

namespace test
{
    public static class MacAddress
    {
        public static string GetMacAddress()
        {
            const int MIN_MAC_ADDR_LENGTH = 12;
            string    macAddress          = string.Empty;
            long      maxSpeed            = -1;

            foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
            {
                string tempMac = nic.GetPhysicalAddress().ToString();
                if (nic.Speed > maxSpeed && !string.IsNullOrEmpty(tempMac) && tempMac.Length >= MIN_MAC_ADDR_LENGTH)
                {
                    maxSpeed   = nic.Speed;
                    macAddress = tempMac;
                }
            }
            return macAddress;
        }
    }
}