How do you determine which adapter is used?

Question

I have a need to figure out which adapter is used when a connection is created. In other words, if I have multiple NIC cards (i.e. wireless, lan, etc) on my machine, which card is being used for the connection?

If anyone can point me in the right direction...

I've got no idea as to the answer, but it'll probably help seeing the code to create the connection. Also, is controlling the NIC the connection uses ok? — George Duckett, Aug 25 '11 at 15:25
You are not going to be able to force your program to use a specfic connection. You should be able to determine which connection it is based on if a particular adapter is active. — Security Hound, Aug 25 '11 at 15:27
possible duplicate of [Identifying active network interface in .NET](http://stackoverflow.com/questions/359596/identifying-active-network-interface-in-net) — Jehof, Jan 09 '13 at 08:05

score 4 · Accepted Answer · answered Aug 25 '11 at 15:31

In C#

foreach(var nic in NetworkInterface.GetAllNetworkInterfaces.Where(n => n.OperationalStatus == OperationStatus.UP)
{
    if(nic.GetIsNetworkAvailable())
    {
       //nic is attached to some form of network
    }
}

VB .NET

ForEach nic in NetworkInterface.GetAllNetworkInterfaces.Where(Function(n) n.OperationalStatus = OperationStatus.UP)
    If nic.GetIsNetworkAvailable() Then
       //nic is attached to some form of network
    End If
Next

This will only test active working Network Interfaces that are connected to an active network.

As you note this only checks that the nic is attached to a network of some sort. I believe that http://stackoverflow.com/questions/359596/identifying-active-network-interface-in-net is a better solution. — Joshua Drake, Jan 08 '13 at 20:00

score 0 · Answer 2 · answered Aug 25 '11 at 15:31

0

Why don't you use the MAC address?

answered Aug 25 '11 at 15:31

Rhyous

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score 0 · Answer 3 · edited May 23 '17 at 12:08

Maybe you could map it by the MAC Address:

var nics = NetworkInterface.GetAllNetworkInterfaces();
foreach (var nic in nics)
{
    if (nic.OperationalStatus == OperationalStatus.Up)
    {
        var mac = nic.GetPhysicalAddress().ToString();
        if (mac == "your:connections:mac:address")
        {
            /* ... */
        }
    }
}

The "your:connections:mac:address" part you can figure out following this method, using the IP address of the LocalEndPoint.

How do I obtain the physical (MAC) address of an IP address using C#?

It's not beautiful, but it could work.

How do you determine which adapter is used?

3 Answers3