使用FCM（Firebase Cloud Messaging）通过C＃将推送发送到iOS

Question

我使用以下C＃代码在IOS设备推送上使用FCM，但IOS设备未收到推送消息。

我使用FCM推送成功推送到IOS设备。

这是我的C＃代码

 try
            {
                //
                string applicationID = "AIzaSyhYzPkQgYND6P5cpLvEMoR9TUbJpgJeks";
                string senderId = "968869743756";
                string deviceId = "/topics/ios";
                WebRequest tRequest = WebRequest.Create("https://fcm.googleapis.com/fcm/send");
                tRequest.Method = "post";
                tRequest.ContentType = "application/json";
                var data = new
                {
                    to = deviceId,
                    notification = new
                    {
                        title = "body",
                        body = "title",
                        sound = "Enabled"
                    }
                };
                var serializer = new JavaScriptSerializer();
                var json = serializer.Serialize(data);
                Byte[] byteArray = Encoding.UTF8.GetBytes(json);
                tRequest.Headers.Add(string.Format("Authorization: key={0}", applicationID));
                tRequest.Headers.Add(string.Format("Sender: id={0}", senderId));
                tRequest.ContentLength = byteArray.Length;
                using (Stream dataStream = tRequest.GetRequestStream())
                {
                    dataStream.Write(byteArray, 0, byteArray.Length);
                    using (WebResponse tResponse = tRequest.GetResponse())
                    {
                        using (Stream dataStreamResponse = tResponse.GetResponseStream())
                        {
                            using (StreamReader tReader = new StreamReader(dataStreamResponse))
                            {
                                String sResponseFromServer = tReader.ReadToEnd();
                                string str = sResponseFromServer;
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                string str = ex.Message;
            }

sResponseFromServer消息始终为

{"message_id":9201392109823459675}

我想念什么吗？ 这是我第一次使用FCM。