StaTaskScheduler (TPL扩展)和WebBrowser控件WPF -错误线程

我想下载一个网站与WebBrowser控件(WPF)在后台和解析网站之后。下载应该是一个"紧密循环"。我只需要源作为字符串。我尝试了下面的代码，没有给我的结果。如果我不使用它与StaTaskScheduler程序似乎冻结在循环期间。有什么想法吗?

谢谢

StaTaskScheduler sta = new StaTaskScheduler(numberOfThreads: 1); 
private void Button1_Click(object sender, RoutedEventArgs e)
        { 
   for (int i = 0; i < 2; i++)
            {
                Task.Factory.StartNew(() =>
                {
                    WebBrowser wb3 = new WebBrowser();
                    wb3.Source = new Uri("MyURL");
                    n++;
                    wb3.LoadCompleted += new LoadCompletedEventHandler(wb_LoadCompleted);
                }, CancellationToken.None, TaskCreationOptions.None, sta);
            }
        }
void wb_LoadCompleted(object sender, NavigationEventArgs e)
    {
 WebBrowser w = sender as WebBrowser;
  HtmlDocument document = new HtmlDocument(w.Document);
blockingCollection.Add(document.Body.OuterHtml);
        Task.Factory.StartNew(
           () =>
           {
               while (!blockingCollection.IsCompleted)
               {
                   string dlcode;
                   Thread.Sleep(500);
                   if (blockingCollection.TryTake(out dlcode))
                   {
    // tb is a TextBox
                         Dispatcher.BeginInvoke(new Action(() => { tb.Text = dlcode; }));
                   }
               }
           }, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default); 

}

Task<string> DownloadStringAsync(Uri address)
{
     TaskCompletionSource<string> tcs = new TaskCompletionSource<string>();
     WebClient client = new WebClient();
     // Note that you can add error checking here by looking at e.Error/etc, and setting the cancel/error in tcs appropriately...
     client.DownloadStringCompleted += (o,e) => tcs.SetResult(e.Result);
     client.DownloadStringAsync(address);
     return tcs.Task;
}