How to get *internet* IP?

Question

Imagine a situation, I have PC with two lan cards, one is connected to internet another is connected to local network, how can I detect IP which is connected to internet wi

Answer 1

in the same direction as Lukas Šalkauskas, a friend of mine and I wrote this code:

   /* digged, built and (here and there) copied "as is" from web, without paying attention to style.
    Please, do not shot us for this. 
   */
public static void DisplayIPAddresses() 
    { 

        Console.WriteLine("\r\n****************************"); 
        Console.WriteLine("     IPAddresses"); 
        Console.WriteLine("****************************"); 


        StringBuilder sb = new StringBuilder(); 
        // Get a list of all network interfaces (usually one per network card, dialup, and VPN connection)      
        NetworkInterface[] networkInterfaces = NetworkInterface.GetAllNetworkInterfaces(); 

        foreach (NetworkInterface network in networkInterfaces) 
        { 

            if (network.OperationalStatus == OperationalStatus.Up ) 
            { 
                if (network.NetworkInterfaceType == NetworkInterfaceType.Tunnel) continue; 
                if (network.NetworkInterfaceType == NetworkInterfaceType.Tunnel) continue; 
                //GatewayIPAddressInformationCollection GATE = network.GetIPProperties().GatewayAddresses; 
                // Read the IP configuration for each network    

                IPInterfaceProperties properties = network.GetIPProperties(); 
                //discard those who do not have a real gateaway  
                if (properties.GatewayAddresses.Count > 0) 
                { 
                    bool good = false; 
                    foreach  (GatewayIPAddressInformation gInfo in properties.GatewayAddresses) 
                    { 
                        //not a true gateaway (VmWare Lan) 
                        if (!gInfo.Address.ToString().Equals("0.0.0.0")) 
                        { 
                            sb.AppendLine(" GATEAWAY "+ gInfo.Address.ToString()); 
                            good = true; 
                            break; 
                        } 
                    } 
                    if (!good) 
                    { 
                        continue; 
                    } 
                } 
                else { 
                    continue; 
                } 
                // Each network interface may have multiple IP addresses        
                foreach (IPAddressInformation address in properties.UnicastAddresses) 
                { 
                    // We're only interested in IPv4 addresses for now        
                    if (address.Address.AddressFamily != AddressFamily.InterNetwork) continue; 

                    // Ignore loopback addresses (e.g., 127.0.0.1)     
                    if (IPAddress.IsLoopback(address.Address)) continue; 

                    if (!address.IsDnsEligible) continue; 
                    if (address.IsTransient) continue;  

                    sb.AppendLine(address.Address.ToString() + " (" + network.Name + ") nType:" + network.NetworkInterfaceType.ToString()     ); 
                } 
            } 
        } 
        Console.WriteLine(sb.ToString()); 
    }