HttpClient.GetAsync fails in background task with lock screen access and both TimeTrigger or MaintenanceTrigger

Question

Client.GetAsync appears to fail for me when running in a background task in my Windows 8 Metro app.

I tried using both a TimeTrigger and a MaintenanceTrigger. It ap

Answer 1

I had a similar problem to you before, and the way I solved it was to have another deferral in the async task. I think the idea is that, whenever you have an async task, you need a deferral. (I'm not sure if it's best practice, but hey, it works)

Code:

    public void Run(IBackgroundTaskInstance taskInstance)
    {
        updateAllTiles(taskInstance);
    }


    public async void updateAllTiles(IBackgroundTaskInstance taskInstance)
    {
        // Need to use a deferral to run async tasks in the background task
        BackgroundTaskDeferral deferral = taskInstance.GetDeferral();

        dosomething(taskInstance);

        deferral.Complete();
    }

    private async void dosomething(IBackgroundTaskInstance taskInstance)
    {
        BackgroundTaskDeferral deferral = taskInstance.GetDeferral();

        HttpClient client = new HttpClient();
        HttpResponseMessage resp = await client.GetAsync(new Uri(url));

        updateTile(resp);

        deferral.Complete();
    }