當我使用webclient時，如何在OpenReadCompletedEvent中獲取URL

Question

當我使用webclient時，如何在OpenReadCompletedEvent中獲取URL。

WebClient webClient = new WebClient(); 
webClient.OpenReadAsync(url);  // in event method I want get this url  
webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(CardInfoDown_Completed); 


private void CardInfoDown_Completed(object sender, OpenReadCompletedEventArgs e) 
    { 
     if (e.Error == null) 
     {   
      using (System.IO.StreamReader reader = new System.IO.StreamReader(e.Result)) 
      { 
       // I want get the url here, 
       // How to do this? 
       string strStream = reader.ReadToEnd();    
      } 
     }   
    } 

謝謝！

Answer 1

WebClient webClient = new WebClient(); 
    webClient.BaseAddress = "http://hhh.com"; 
    webClient.OpenReadAsync(new Uri("http://hhh.com"));  // in event method I want get this url  
    webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(CardInfoDown_Completed); 

和：

private void CardInfoDown_Completed(object sender, OpenReadCompletedEventArgs e) 
{ 
    if (e.Error == null) 
    { 
     using (System.IO.StreamReader reader = new System.IO.StreamReader(e.Result)) 
     { 
      // I want get the url here, 
      // How to do this? 
      var client = sender as WebClient; 
      if (client != null) 
      { 
       var url = client.BaseAddress; //returns hhh.com 
      } 
      string strStream = reader.ReadToEnd(); 
     } 
    } 

Answer 2

安東西濟科夫的解決方案是好的，但如果URL是絕對只會工作（如http://hhh.com）。如果使用相對URL，.NET將自動將基地址與相對URL合併（因此可能導致無效URL）。

傳送價值給OpenReadCompleted事件處理程序，你應該利用這個OpenRead過載提供自定義令牌（在這種情況下，您的網址）：http://msdn.microsoft.com/en-us/library/ms144212(v=vs.95).aspx

WebClient webClient = new WebClient(); 
webClient.OpenReadAsync(new Uri("http://hhh.com"), "http://hhh.com"); 
webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(CardInfoDown_Completed); 

然後檢索值：

private void CardInfoDown_Completed(object sender, OpenReadCompletedEventArgs e) 
{ 
    if (e.Error == null) 
    { 
     using (System.IO.StreamReader reader = new System.IO.StreamReader(e.Result)) 
     { 
      var url = (string)e.UserState; 
      string strStream = reader.ReadToEnd(); 
     } 
    } 
} 

Answer 3

對我來說，甚至從上面的簡單變化工作正常

private void CardInfoDown_Completed(object sender, DownloadStringCompletedEventArgs e) 
    { 
     string url; 

     if (e.Error == null) 
     { 
      url = (string)e.UserState; 
     } 
     // ... 
    }