C# windows phone 8中的toast通知-流错误

我已从microsoft站点下载了toast通知示例代码，但代码执行不正确--在httpwebresponse中出现错误--

protectedvoid按钮sendtoos\u单击（对象发送者，事件参数e）
{
尝试
{
//获取Microsoft推送通知服务在创建通知通道时返回给推送客户端的Uri。
//通常，web服务将侦听来自web客户端的Uri，并维护要发送的Uri列表
//通知发送到。
string subscriptionUri=TextBoxUri.Text.ToString（）；
HttpWebRequest sendNotificationRequest=（HttpWebRequest）WebRequest.Create（subscriptionUri）；
//我们将创建一个HTTPWebRequest，将toast通知发布到Microsoft推送通知服务。
//HTTP POST是唯一允许发送通知的方法。
sendNotificationRequest.Method=“POST”；
//可选的自定义标头X-MessageID唯一标识通知消息。
//如果存在，则在通知响应中返回//相同的值。该值必须是包含UUID的字符串。
//sendNotificationRequest.Headers.Add（“X-MessageID”，即“）；
//创建toast消息。
字符串toastMessage=“”+
"" +
"" +
“”+TextBoxTitle.Text.ToString（）+“”+
“”+TextBoxSubTitle.Text.ToString（）+“”+
“/Page2.xaml？NavigatedFrom=Toast通知”+
" " +
"";
//设置要发送的通知有效负载。
byte[]notificationMessage=Encoding.Default.GetBytes（toastMessage）；
//设置web请求内容长度。
sendNotificationRequest.ContentLength=notificationMessage.Length；
sendNotificationRequest.ContentType=“text/xml”；
sendNotificationRequest.Headers.Add（“X-WindowsPhone-Target”、“toast”）；
sendNotificationRequest.Headers.Add（“X-NotificationClass”，“2”）；
使用（Stream requestStream=sendNotificationRequest.GetRequestStream（））
{
Write（notificationMessage，0，notificationMessage.Length）；
}
//发送通知并获取响应。
HttpWebResponse=（HttpWebResponse）sendNotificationRequest.GetResponse（）；//此行出现异常
字符串notificationStatus=response.Headers[“X-notificationStatus”]；
字符串notificationChannelStatus=response.Headers[“X-SubscriptionStatus”]；
字符串deviceConnectionStatus=response.Headers[“X-deviceConnectionStatus”]；
//显示来自Microsoft推送通知服务的响应。
//通常，错误处理代码在这里。在现实世界中，由于数据连接并不总是可用，
//如果无法访问设备，则可能需要限制通知。
Text=notificationStatus+“|”+设备连接状态+“|”+notificationChannelStatus；
}
捕获（例外情况除外）
{
TextBoxResponse.Text=“发送更新时发现异常：”+ex.ToString（）；
}
}

}

我曾尝试在VS2010和VS2013 express中运行此代码，但仍然出现相同的错误

    protected void ButtonSendToast_Click(object sender, EventArgs e)
{
  try
  {
    // 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 Uri's coming from the web client and maintain a list of Uri's to send
    // notifications out to.
    string subscriptionUri = TextBoxUri.Text.ToString();


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

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

    // The optional custom header X-MessageID uniquely identifies a notification message. 
    // If it is present, the // same value is returned in the notification response. It must be a string that contains a UUID.
    // sendNotificationRequest.Headers.Add("X-MessageID", "<UUID>");

    // Create the toast message.
    string toastMessage = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
    "<wp:Notification xmlns:wp=\"WPNotification\">" +
       "<wp:Toast>" +
            "<wp:Text1>" + TextBoxTitle.Text.ToString() + "</wp:Text1>" +
            "<wp:Text2>" + TextBoxSubTitle.Text.ToString() + "</wp:Text2>" +
            "<wp:Param>/Page2.xaml?NavigatedFrom=Toast Notification</wp:Param>" +
       "</wp:Toast> " +
    "</wp:Notification>";

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

    // Sets the web request content length.
    sendNotificationRequest.ContentLength = notificationMessage.Length;
    sendNotificationRequest.ContentType = "text/xml";
    sendNotificationRequest.Headers.Add("X-WindowsPhone-Target", "toast");
    sendNotificationRequest.Headers.Add("X-NotificationClass", "2");

    using (Stream requestStream = sendNotificationRequest.GetRequestStream())
    {
        requestStream.Write(notificationMessage, 0, notificationMessage.Length);
    }

    // Send the notification and get the response.
    HttpWebResponse response = (HttpWebResponse)sendNotificationRequest.GetResponse();   // Exception in this line
    string notificationStatus = response.Headers["X-NotificationStatus"];
    string notificationChannelStatus = response.Headers["X-SubscriptionStatus"];
    string deviceConnectionStatus = response.Headers["X-DeviceConnectionStatus"];

    // Display the response from the Microsoft Push Notification Service.  
    // Normally, error handling code would be here.  In the real world, because data connections are not always available,
    // notifications may need to be throttled back if the device cannot be reached.
    TextBoxResponse.Text = notificationStatus + " | " + deviceConnectionStatus + " | " + notificationChannelStatus;
  }
  catch (Exception ex)
  {
    TextBoxResponse.Text = "Exception caught sending update: " + ex.ToString();
  }

}