private IAsyncResult BeginTask(object sender, EventArgs e, AsyncCallback cb, object state)
    {
        Debug.WriteLine(pageID + "Begin Task: " + System.Threading.Thread.CurrentThread.ManagedThreadId);

        start = new System.Threading.ThreadStart(DoSomethingSlow);
        System.Threading.Thread.Sleep(TimeSpan.FromSeconds(10));
        return(start.BeginInvoke(cb, state));
    }