My application use Web-service. I'm control from what workstation was request and for this send MAC-Address how parameter of all methods. But then I start testing application in real, I found workstations which have many network adapters - Ethernet, Wireless, Bluetooth. When I get MAC-address using next code: var networkAdapters = NetworkInterface.GetAllNetworkInterfaces(); if (networkAdapters == null || networkAdapters.Length == 0) return string.Empty; string address = string.Empty; foreach (var adapter in networkAdapters) { var a = adapter.GetPhysicalAddress(); if (a != null && a.ToString() != string.Empty) { address = a.ToString(); break; } } return address; Sometimes Web-service receive from workstation different MAC-Addresses, but I want get always only one MAC-address. Please, help me.