UWP (Windows 10) Background Task - Error HRESULT E_FAIL has been returned from a call to a COM component (VS2017)

Question

I have a UWP Windows 10 app intended to function as a SignalR client. I had this working before, but recently started getting this error: Error HRESULT E_FAIL has been returned from a call to a COM component. Not sure what changed, nothing in weird in source control. It comes up when I try to trigger a background task via an ApplicationTrigger.

Here is the code in my App.XML:

private void SignalR()
{
    _hubConnection = new HubConnection("http://localhost/hollerhub");
    _hubConnection.Credentials = CredentialCache.DefaultCredentials;
    _toast = _hubConnection.CreateHubProxy("toast");
    _toast.On<string>("broadcastMessage", msg =>
    {
        var localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
        localSettings.Values["toastInfo"] = msg;
        var appTrigger = new ApplicationTrigger();
        appTrigger.RequestAsync().GetResults();  // <--- This is where the error is thrown
    });

    _hubConnection.Start(); 
}

The background task is registered at app start, but the ApplicationTrigger is not reaching my background task code before failing. It is receiving the SignalR message just fine.

Answer 1

The problem was I had background tasks disabled for this app in my Windows 10 Privacy Settings.

System Settings => Privacy Settings => Background Apps

I discovered this during my background task registration as BackgroundExecutionManager.RequestAccessAsync() was returning BackgroundAccessStatus.DeniedBySystemPolicy.