WebClient.DownloadProgressChanged not working?

Question

I am using Windows Phone to download a file with a WebClient. The DownloadProgressChanged event does not work. It fires only once, returning a value of "4923206" for DownloadProgressChangedEventArgs.BytesRecieved. My code is:

    private void listBox1_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        WebClient wb = new WebClient();
        wb.DownloadProgressChanged += wbchange;
        wb.OpenReadAsync(new Uri("http://sohowww.nascom.nasa.gov/data/LATEST/current_eit_304small.gif"));
    }

    private void wbchange(object sender, DownloadProgressChangedEventArgs e)
    {
        MessageBox.Show(e.BytesReceived.ToString()); (obviously in the end I will not be showing a message at every change)
    }

What is wrong with this?

Answer 1

It's working absolutely fine, it just happens to have downloaded all the bytes on the first DownloadProgressChanged invoke.

If you read the documentation you'll see that this is the expected behaviour.