DownloadStringAysnc - 不显示进度

Question

VS 2008 SP1

我正在使用DownloadStringAysnc。但是，ProgressChanged事件直到字符串被下载后才显示进度。

即使当我尝试下载包含在大文件中的字符串时。程序仍然是响应，所以我知道它正在做一些事情。但是，progressChanged事件触发完成后，进度已经完成。

我知道这是progressChanged和DownloadStringCompleted之后立即触发。但是，它们应该是一个暂停，因为该文件相当大。

这是我目前使用的代码片段。和下面的输出。奇怪的是，e.progresspercentage是100％。似乎被召唤了两次。

非常感谢任何意见，

Output in the progress changed event 
Progress changed Version userstate: [ Version1 ] 
progressBar1.Value [ 100 ] 
Progress changed Version userstate: [ Version1 ] 
progressBar1.Value [ 100 ] 
Completed Version userstate: [ Version1 ] 


private void UpdateAvailable() 
     { 
      WebClient wbCheckUpdates = new WebClient(); 
      wbCheckUpdates.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wbCheckUpdates_DownloadProgressChanged); 
      wbCheckUpdates.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wbCheckUpdates_DownloadStringCompleted); 
      DownloadFiles df = new DownloadFiles(); 
      string webServerURL = df.webServerPath; 

      wbCheckUpdates.DownloadStringAsync(new Uri(Path.Combine(webServerURL, "version.txt")), "Version1"); 
     } 




void wbCheckUpdates_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e) 
     { 
      Console.WriteLine("Progress version changed userstate: [ " + e.UserState + " ]"); 
      progressBar1.Value = e.ProgressPercentage; 
      Console.WriteLine("progressBar1.Value [ " + this.progressBar1.Value + " ]"); 
     } 

void wbCheckUpdates_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) 
     { 
      Console.WriteLine("Completed version userstate: [ " + e.UserState + " ]"); 
     } 

===========使用编辑DownloadDataAysnc ===============

wbCheckUpdates.DownloadDataAsync(new Uri(Path.Combine(webServerURL, "version.txt")), "Version1"); 


void wbCheckUpdates_DownloadDataCompleted(object sender, DownloadDataCompletedEventArgs e) 
     { 
      byte[] result = e.Result;   
      Console.WriteLine("Completed data: [ " + System.Text.ASCIIEncoding.Default.GetString(result) + " ]"); 
     } 

的结果是一样的：

Progress changed Version userstate: [ Version1 ] 
progressBar1.Value [ 100 ] 
Progress changed Version userstate: [ Version1 ] 
progressBar1.Value [ 100 ] 
Completed data: [ 1.0.11 ] 

Answer 1

根据该文件，DownloadStringAsync根本不报告进度。请参阅WebClient.DownloadProgressChanged Event的文档。