How to get Router MAC address in .Net (C#)

You can never get the MAC address of a user connected to your website, when a socket connection occurs between the destination (your website's server) and a source (client's computer) you can only get the source IP address, for the MAC address it's never sent over the socket connection (Client <--> Server), in order to get the IP address of a user:

using System.Net;

Private string GetIP()
{
string strHostName = "";
strHostName = System.Net.Dns.GetHostName();

IPHostEntry ipEntry = System.Net.Dns.GetHostEntry(strHostName);

IPAddress[] addr = ipEntry.AddressList;

return addr[addr.Length-1].ToString();

}