var subscription = await PushManager.SubscribeAsync("YOUR_PUBLIC_KEY", "myChannel1");

var subscriptionJson = subscription.ToJson();

// TODO: Display the subscriptionJson or send that to your push server

public App()
{
    this.InitializeComponent();
    this.Suspending += OnSuspending;

    // Call the new method
    RegisterPushBackgroundTask();
}

// New method
private void RegisterPushBackgroundTask()
{
    try
    {
        const string PushBackgroundTaskName = "Push";
        if (!BackgroundTaskRegistration.AllTasks.Any(i => i.Value.Name == PushBackgroundTaskName))
        {
            var builder = new BackgroundTaskBuilder();
            builder.Name = PushBackgroundTaskName;
            builder.SetTrigger(new PushNotificationTrigger());
            builder.Register();
        }
    }
    catch (Exception ex)
    {
    }
}

// New method
protected override void OnBackgroundActivated(BackgroundActivatedEventArgs args)
{
    // We need to get a deferral since we'll be doing async code
    var deferral = args.TaskInstance.GetDeferral();

    try
    {
        RawNotification notification = (RawNotification)args.TaskInstance.TriggerDetails;

        // Decrypt the content
        string payload = await PushManager.GetDecryptedContentAsync(notification);

        // Show a notification
        // You'll need Microsoft.Toolkit.Uwp.Notifications NuGet package installed for this code
        ToastContent content = new ToastContent()
        {
            Visual = new ToastVisual()
            {
                BindingGeneric = new ToastBindingGeneric()
                {
                    Children =
                    {
                        new AdaptiveText()
                        {
                            Text = "Push notification received"
                        },

                        new AdaptiveText()
                        {
                            Text = payload
                        }
                    }
                }
            }
        };

        ToastNotificationManager.CreateToastNotifier().Show(new ToastNotification(content.GetXml()));
    }
    catch
    {
        // Decryption probably failed, did your server use the correct keys to sign?
    }

    // Complete the deferral, telling the OS that we're done
    deferral.Complete();
}

public static class WebPush
{
    // Keys generated from step #3 (don't store private in public source code)
    // Note that this is the same public key you include in your app in step #4
    private const string PublicKey = "BGg3UxX...";
    private const string PrivateKey = "_RwmE...";

    private static WebPushClient _webPushClient = new WebPushClient();

    public class Subscription
    {
        public string Endpoint { get; set; }
        public SubscriptionKeys Keys { get; set; }
    }

    public class SubscriptionKeys
    {
        public string P256DH { get; set; }
        public string Auth { get; set; }
    }

    public static async Task SendAsync(string subscriptionJson, string payload)
    {
        var subscription = JsonConvert.DeserializeObject<Subscription>(subscriptionJson);

        try
        {
            await _webPushClient.SendNotificationAsync(
                subscription: new PushSubscription(
                    endpoint: subscription.Endpoint,
                    p256dh: subscription.Keys.P256DH,
                    auth: subscription.Keys.Auth),
                payload: payload,
                vapidDetails: new VapidDetails(
                    subject: "mailto:[email protected]",
                    publicKey: PublicKey,
                    privateKey: PrivateKey));
        }
        catch (Exception ex)
        {
            Debugger.Break();
            throw ex;
        }
        return;
    }
}