Identifying active network interface

Question

In a .NET application, how can I identify which network interface is used to communicate to a given IP address?

I am running on workstations with multiple network in

Answer 1

At least you can start with that, giving you all addresses from dns for the local machine.

IPHostEntry hostEntry = Dns.GetHostEntry(Environment.MachineName);

foreach (System.Net.IPAddress address in hostEntry.AddressList)
{
    Console.WriteLine(address);
}