Question

What is the best way to determine whether there is an available Internet connection for a WinForms app. (Programatically of course) I want to disable/hide certain functions if the user is not connected to the Internet.

Answer 1

The following will determine if you are connected to a network, however, that doesn’t necessarily mean that you are connected to the Internet:

NetworkInterface.GetIsNetworkAvailable()  

Here is a C# translation of Steve’s code that seems to be pretty good:

private static int ERROR_SUCCESS = 0; public static bool IsInternetConnected() {     long dwConnectionFlags = 0;     if (!InternetGetConnectedState(dwConnectionFlags, 0))         return false;      if(InternetAttemptConnect(0) != ERROR_SUCCESS)         return false;      return true; }    [DllImport('wininet.dll', SetLastError=true)]  public static extern int InternetAttemptConnect(uint res);    [DllImport('wininet.dll', SetLastError=true)]   public static extern bool InternetGetConnectedState(out int flags,int reserved);