出现InvalidOperationException与BeginGetRequestStream

Question

我收到以下错误：

System.InvalidOperationException was unhandled by user code 
    HResult=-2146233079 
    Message=Operation is not valid due to the current state of the object. 
    Source=System.Windows 
    StackTrace: 
     at System.Net.Browser.ClientHttpWebRequest.InternalEndGetRequestStream(IAsyncResult asyncResult) 
     at System.Net.Browser.ClientHttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult) 
     at SophosMobileControl.MainPage.<>c__DisplayClass5.<PushTestButton_Click>b__3(IAsyncResult ar) 
     at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClass18.<InvokeGetRequestStreamCallback>b__16(Object state2) 
    InnerException: 

与folowwing代码：

// Get the URI that the Microsoft Push Notification Service returns to the push client when creating a notification channel. 
      // Normally, a web service would listen for URIs coming from the web client and maintain a list of URIs to send 
      // notifications out to. 
      string subscriptionUri = (App.Current.Resources["Locator"] as ViewModelLocator).Main.PushUri; 

      HttpWebRequest sendNotificationRequest = (HttpWebRequest)WebRequest.Create(subscriptionUri); 

      // Create an HTTPWebRequest that posts the toast notification to the Microsoft Push Notification Service. 
      // HTTP POST is the only method allowed to send the notification. 
      sendNotificationRequest.Method = "POST"; 

      // Create the toast message. 
      string toastMessage = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" + 
      "<wp:Notification xmlns:wp=\"WPNotification\">" + 
       "<wp:Toast>" + 
        "<wp:Text1>" + "Title" + "</wp:Text1>" + 
        "<wp:Text2>" + "Subtitle" + "</wp:Text2>" +       
       "</wp:Toast> " + 
      "</wp:Notification>"; 

      // Set the notification payload to send. 
      byte[] notificationMessage = Encoding.UTF8.GetBytes(toastMessage); 

      // Set the web request content length. 
      sendNotificationRequest.ContentLength = notificationMessage.Length; 
      sendNotificationRequest.ContentType = "text/xml"; 

      //sendNotificationRequest.Headers["X-WindowsPhone-Target"] = "toast"; 
      //sendNotificationRequest.Headers["X-NotificationClass"] = "2"; 

      sendNotificationRequest.BeginGetRequestStream(ar => 
      { 
       using (Stream postStream = sendNotificationRequest.EndGetRequestStream(ar)) 
       { 
        postStream.Write(notificationMessage, 0, notificationMessage.Length); 
       } 
      }, sendNotificationRequest); 

Answer 1

我的解决办法是改变下面的代码：按照

 sendNotificationRequest.BeginGetRequestStream(ar => 
     { 
      using (Stream postStream = sendNotificationRequest.EndGetRequestStream(ar)) 
      { 
       postStream.Write(notificationMessage, 0, notificationMessage.Length); 
      } 
     }, sendNotificationRequest); 

：

sendNotificationRequest.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), sendNotificationRequest); 

    void GetRequestStreamCallback(IAsyncResult callbackResult) 
    { 
     HttpWebRequest myRequest = (HttpWebRequest)callbackResult.AsyncState; 
     // End the stream request operation 
     Stream postStream = myRequest.EndGetRequestStream(callbackResult); 

     // Add the post data to the web request 
     postStream.Write(notificationMessage, 0, notificationMessage.Length); 
     postStream.Close(); 
    }