Tip: Detectar el estado de la red con .NET

namespace Examples.Net.AddressChanges
{
    public class NetworkingExample
    {
        public static void Main()
        {
            NetworkChange.NetworkAddressChanged += new
                NetworkAddressChangedEventHandler(AddressChangedCallback);
            NetworkChange.NetworkAvailabilityChanged += new
                NetworkAvailabilityChangedEventHandler(NetworkChange_NetworkAvailabilityChanged);
            Console.ReadLine();
        }

        static void NetworkChange_NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e)
        {
            Console.WriteLine(e.IsAvailable);
        }
        static void AddressChangedCallback(object sender, EventArgs e)
        {
            NetworkInterface[] adapters = NetworkInterface.GetAllNetworkInterfaces();
            foreach (NetworkInterface adapter in adapters)
            {
                Console.WriteLine("   {0} is {1}", adapter.Name, adapter.OperationalStatus);
            }
        }
    }
}