Question

I wrote this function to check if an internet connection is available:

    bool IsOnline()
    {
        try
        {
            var request = (HttpWebRequest)WebRequest.CreateHttp("http://www.google.com/");
            request.Timeout = 2000;

            var response = (HttpWebResponse)request.GetResponse();
            return ((int)response.StatusCode) < 400;
        }
        catch (Exception) { return false; }      
    }

It seems to work in almost all cases however under my work network it return false after a timeout error while the connection is available.

Note:
– this function return false but I can go online with a webbrowser component in my WPF application
– the connection is pretty good. (so it is impossible to spend more than 2sec in loading google.com)
– I’m behind a proxy configured correctly in Control Panel/Internet Options/Connection

Any ideas?

Answer 1

As workaround I changed my function in this way:

bool IsOnline()
{
    try
    {
        var request = (HttpWebRequest)WebRequest.CreateHttp("http://www.google.com/");
        request.Timeout = 2000;

        var registry = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Windows\\CurrentVersion\\Internet Settings", false);
        var proxy = (string)registry.GetValue("ProxyServer");
        var isProxyEnabled = (int)registry.GetValue("ProxyEnable");
        if (isProxyEnabled>0)
        {
            request.Proxy = new WebProxy(proxy, true, null, System.Net.CredentialCache.DefaultNetworkCredentials);
        }

        var response = (HttpWebResponse)request.GetResponse();
        return ((int)response.StatusCode) < 400;
    }
    catch (Exception) { return false; }      
}

If I try to use WebRequest.GetSystemWebProxy() I get a IWebProxy (WrappedWebProxy) that has the same settings as the one that I manually build but it does not work. It recognize all addresses as local also if I do not have check the “Bypass proxy server for local addresses”.

Then if I change through the debugger the bypasslocal flag it works. It’s so strange that looks like a bug.