Windows Phone 7.1 HTTP GET与DownloadStringAsync

Question

在网上搜索大约4小时后，我仍然不明白Windows Phone 7上的异步函数。我试图运行该代码，但它看起来像我的webClient的事件“DownloadStringCompleted”从未被提出。我试图在这里等待一个答案，但它只是冻结我的应用程序。任何人都可以帮忙解释为什么它不起作用？

internal string HTTPGet() 
    { 
     string data = null; 
     bool exit = false; 
     WebClient webClient = new WebClient(); 
     webClient.UseDefaultCredentials = true; 

     webClient.DownloadStringCompleted += (sender, e) => 
     { 
      if (e.Error == null) 
      { 
       data = e.Result; 
       exit = true; 
      } 
     }; 

     webClient.DownloadStringAsync(new Uri(site, UriKind.Absolute)); 

     //while (!exit) 
     // Thread.Sleep(1000); 

     return data; 
    } 

好的。找到点东西！ http://blogs.msdn.com/b/kevinash/archive/2012/02/21/async-ctp-task-based-asynchronous-programming-for-windows-phone.aspx 耶！ :)

Answer 1

它不是模拟器的问题。你想从你的HttpGet（）方法中返回数据，但是在来自webClient的实际响应发生之前，数据已经被返回（为空）。因此我建议您对代码进行一些更改并尝试。

WebClient client = new WebClient(); 
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted); 
client.DownloadStringAsync(new Uri(site, UriKind.Absolute)); 

然后在DownloadCompleted事件处理程序（或回调），您manupulate实际结果

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) 
{ 
    var response= e.Result; // Response obtained from the site 
}