DownloadStringAsync（）不會異步下載字符串

Question

嘗試執行downloadStringAsync()以防止UI凍結10秒當下載一個字節的數據。但是，即使下載完成，它也會凍結UI，就像我使用downloadString()一樣。

這裏是我的代碼：

public void loadHTML() 
    { 
      WebClient client = new WebClient(); 

      // Specify that the DownloadStringCallback2 method gets called 
      // when the download completes. 
      client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(loadHTMLCallback); 
      client.DownloadStringAsync(new Uri("http://www.example.com")); 
      return; 
    } 

    public void loadHTMLCallback(Object sender, DownloadStringCompletedEventArgs e) 
    { 
     // If the request was not canceled and did not throw 
     // an exception, display the resource. 
     if (!e.Cancelled && e.Error == null) 
     { 
      string result = (string)e.Result; 

      // Do cool stuff with result 

     } 
    } 

Answer 1

遇到同樣的問題，並找到了解決辦法。 這裏很複雜的討論： http://social.msdn.microsoft.com/Forums/en-US/a00dba00-5432-450b-9904-9d343c11888d/webclient-downloadstringasync-freeze-my-ui?forum=ncl

總之，問題是Web客戶端正在搜索代理服務器並掛起應用程序。 以下解決方案可幫助：

WebClient webClient = new WebClient(); 
webClient.Proxy = null; 
... Do whatever else ...