Send cross-platform notifications with Azure Notification Hubs

This tutorial builds on the previous tutorial, Send notifications to specific users by using Azure Notification Hubs. That tutorial describes how to push notifications to all devices that are registered to a specific authenticated user. That approach required multiple requests to send a notification to each supported client platform. Azure Notification Hubs supports templates, with which you can specify how a specific device wants to receive notifications. This method simplifies sending cross-platform notifications.

This article demonstrates how to take advantage of templates to send a notification that targets all platforms. This article uses a single request to send a platform neutral notification. For more detailed information about templates, see Notification Hubs overview.

Send cross-platform notifications using templates

This section uses the sample code you built in the Send notifications to specific users by using Azure Notification Hubs tutorial. You can download the complete sample from GitHub.

To send cross-platform notifications using templates, do the following:

1. In Visual Studio in Solution Explorer, expand the Controllers folder, and then open the RegisterController.cs file.

2. Locate the block of code in the Put method that creates a new registration, and then replace the switch content with the following code:

   switch (deviceUpdate.Platform)
   {
       case "mpns":
           var toastTemplate = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
               "<wp:Notification xmlns:wp=\"WPNotification\">" +
                   "<wp:Toast>" +
                       "<wp:Text1>$(message)</wp:Text1>" +
                   "</wp:Toast> " +
               "</wp:Notification>";
           registration = new MpnsTemplateRegistrationDescription(deviceUpdate.Handle, toastTemplate);
           break;
       case "wns":
           toastTemplate = @"<toast><visual><binding template=""ToastText01""><text id=""1"">$(message)</text></binding></visual></toast>";
           registration = new WindowsTemplateRegistrationDescription(deviceUpdate.Handle, toastTemplate);
           break;
       case "apns":
           var alertTemplate = "{\"aps\":{\"alert\":\"$(message)\"}}";
           registration = new AppleTemplateRegistrationDescription(deviceUpdate.Handle, alertTemplate);
           break;
       case "fcm":
           var messageTemplate = "{\"data\":{\"message\":\"$(message)\"}}";
           registration = new FcmTemplateRegistrationDescription(deviceUpdate.Handle, messageTemplate);
           break;
       default:
           throw new HttpResponseException(HttpStatusCode.BadRequest);
   }
   

   This code calls the platform-specific method to create a template registration instead of a native registration. Because template registrations derive from native registrations, you don't need to modify existing registrations.

3. In Solution Explorer, in the Controllers folder, open the NotificationsController.cs file. Replace the Post method with the following code:

   public async Task<HttpResponseMessage> Post()
   {
       var user = HttpContext.Current.User.Identity.Name;
       var userTag = "username:" + user;
   
       var notification = new Dictionary<string, string> { { "message", "Hello, " + user } };
       await Notifications.Instance.Hub.SendTemplateNotificationAsync(notification, userTag);
   
       return Request.CreateResponse(HttpStatusCode.OK);
   }
   

   This code sends a notification to all platforms at the same time. You don't specify a native payload. Notification Hubs builds and delivers the correct payload to every device with the provided tag value, as specified in the registered templates.

4. Republish your Web API project.

5. Run the client app again to verify that the registration has succeeded.

6. Optionally, deploy the client app to a second device, and then run the app. A notification is displayed on each device.

Next steps

Now that you've completed this tutorial, find out more about Notification Hubs and templates in these articles:

• For a different scenario for using templates, see the Push notifications to specific Windows devices running Universal Windows Platform applications tutorial.
• For more detailed information on templates, see Notification Hubs Overview.