Why is GetIsNetworkAvailable() always returning true?

From msdn:

There are many cases in which a device or computer is not connected to a useful network but is still considered available and GetIsNetworkAvailable will return true.

One of these examples could be your case:

For example, if the device running the application is connected to a wireless network that requires a proxy, but the proxy is not set, GetIsNetworkAvailable will return true. Another example of when GetIsNetworkAvailable will return true is if the application is running on a computer that is connected to a hub or router where the hub or router has lost the upstream connection.

I think this method is more appropriate:

   public static bool getIsInternetAccessAvailable()
    {
        switch(NetworkInformation.GetInternetConnectionProfile().GetNetworkConnectivityLevel())
        {
            case NetworkConnectivityLevel.InternetAccess:
                return true;
            default:
                return false;
        }
    }

Note that we are using the Windows.Networking.Connectivity.NetworkInformation and not the System.Net.NetworkInformation namespace.

public bool checkInternetAccess()
{
    var connectivityLevel = Windows.Networking.Connectivity.NetworkInformation
                           .GetInternetConnectionProfile().GetNetworkConnectivityLevel();

    return connectivityLevel == NetworkConnectivityLevel.InternetAccess;
}

Basically what ventura8 said. I would comment his solution, mentioning the namespaces, but I lack enough reputation.

Please correct me if I am wrong but as far as I can see the method you are using is checking network connectivity and not necessarily internet connectivity. I would assume if you are on a network of any sort this would return true regardless of the internet being available or not? See this.

I have noticed that one way of checking for internet connectivity is as follows:

private bool IsInternetAvailable()
{
    try
    {
        Dns.GetHostEntry("www.google.com"); //using System.Net;
        return true;
    } catch (SocketException ex) {
        return false;
    }
}

The above code can be found (in VB.Net by reading the comment from Joacim Andersson [MVP]) in the following post.

Note: The latest edit was suggested by AceInfinity but was rejected in community review. My reputation is too low to override this so I made the change myself.