.NET中的WebBrowser和线程问题

我目前正在从URL列表中读取HTML源代码，该URL使用JavaScript加载带有需要提取的动态超链接的特定span。除了两个小错误外，一切都很好，但可以在调试过程中处理：

1. 当到达DocumentCompleted事件时，有时Document.Body为空

2. 当调用t.Join()时，程序有时会挂起很长一段时间。

   public class WebProcessor
   {
   private string GeneratedSource { get; set; }
   private string URL { get; set; }
   public string GetGeneratedHTML(string url)
   {
       URL = url;
       Thread t = new Thread(new ThreadStart(WebBrowserThread));
       t.SetApartmentState(ApartmentState.STA);
       t.Start();
       t.Join(); 
       return GeneratedSource;
    //When GetGeneratedHTML() is called more than once there is a chance the program 
   //will hang indefinitely maybe even deadlock??
   }
   private void WebBrowserThread()
   {
       WebBrowser wb = new WebBrowser();
      wb.Navigate(URL);
       wb.DocumentCompleted +=
           new WebBrowserDocumentCompletedEventHandler(
               wb_DocumentCompleted);
       while (wb.ReadyState != WebBrowserReadyState.Complete)
           Application.DoEvents();
       wb.Dispose();
   }
   private void wb_DocumentCompleted(object sender,
       WebBrowserDocumentCompletedEventArgs e)
   {
       if(((WebBrowser)sender).Document.Body != null)
       {
           GeneratedSource = ((WebBrowser)sender).Document.Body.InnerHtml;
       }
       else
       {
   //Handle when Document isn't fully loaded
       }
   }
   }