Exception caught sending update: System.NullReferenceException: Object reference not set to an instance of an object

Question

I added push notification handling codes to my xamarin forms UWP application.

Codes:

async Task InitRemoteNotificationAsync()
    {
        var channel = await PushNotificationChannelManager.CreatePushNotificationChannelForApplicationAsync();
        if (channel != null)
        {
            channel.PushNotificationReceived += OnPushNotificationReceived;
            Debug.WriteLine($"Received token:{channel.Uri}");
        }
    }

private void OnPushNotificationReceived(PushNotificationChannel sender, PushNotificationReceivedEventArgs args)
    {

        if (args.ToastNotification.Content.InnerText != null)
        {
            var msg = args.ToastNotification.Content.InnerText;
            Xamarin.Forms.MessagingCenter.Send<object, string>(this, MyProject.App.NotificationReceivedKey, msg);
        }
    }

I have added null checks in my codes. When I try to push a test notification from the http://pushtestserver.azurewebsites.net/wns/ getting the following exception.

Exception caught sending update: System.NullReferenceException: Object reference not set to an instance of an object. at WebRole1.WNS.WebForm1.PostToWns(String secret, String sid, String uri, String xml, String notificationType, String contentType) at WebRole1.WNS.WebForm1.btnDiyPush_Click(Object sender, EventArgs e)

Screenshot:

So how is your `btnDiyPush_Click` method implemented? According to the stacktrace, the exception is raised within this method. — mm8, Mar 12 '19 at 08:56
@mm8 I don't have any method named `btnDiyPush_Click` in my code. — Sreejith Sree, Mar 12 '19 at 12:29
I have added all the codes for handling push notification. When I push notification from http://pushtestserver.azurewebsites.net/wns/ I am getting this exception — Sreejith Sree, Mar 12 '19 at 12:42
I am getting this exception on http://pushtestserver.azurewebsites.net/wns/ — Sreejith Sree, Mar 12 '19 at 12:42
At where? If web role at pushtestserver.azurewebsites.net/wns/ throws an exception, there is not much you can do about it in the receiving client app. — mm8, Mar 12 '19 at 12:43

score 1 · Accepted Answer · answered Mar 12 '19 at 12:45

The exception is obviously thrown in the web role, before the message is sent to your app.

There is nothing you can do about this the receiving client app. Your code is never executed. The fix has to be applied to the web role. Create your own one or use one that actually works.

Exception caught sending update: System.NullReferenceException: Object reference not set to an instance of an object

1 Answers1