C# JSON Requests and Responses for Windows Phone 7.1 app

Question

I'm trying to implement https://gist.github.com/jgable/881673 I have already posted my question there, could you please help me to get a result? The problem is that in

private void Button_Click(object sender, RoutedEventArgs e)
{
    (new TestService()).StartService(
        resp =>
        {
            MessageBox.Show(resp.Data, "Response", MessageBoxButton.OK);
        },
        err =>
        {
            MessageBox.Show(err.Message, "Error", MessageBoxButton.OK);
        });
}

the resp.Data does not return the JSON response so I cannot get the response and continue with my login process.

Thanks in advance /magefi