Get MAC address of client machine using C#

using System.Management;

String query = "select MacAddress FROM Win32_NetworkAdapter";
ObjectQuery objQuery = new ObjectQuery(query);
ManagementObjectSearcher moSearcher = new ManagementObjectSearcher(objQuery);
string macAddress = string.Empty;
foreach (ManagementObject obj in moSearcher.Get())
{
if(macAddress==string.Empty){
macAddress = obj["MACAddress"].ToString();
obj.Dispose();
}
}
MessageBox.Show(macAddress.ToString());

Note: Add System.Management in reference
(Solution Explorer --> Add Reference --> .NET --> System.Management )