Handle error at non-UI thread - windows-8

Question

For some reason unhandled exception which occur at non-UI thread don't handled by App_UnhandledException handler.
This approach works well for Windows Phone apps to globally handle, track and analyze exceptions but doesn't work for Windows 8 apps.
this.UnhandledException += App_UnhandledException; //doesn't handle
private void Button_Click_1(object sender, RoutedEventArgs e)
{
var task = new Task(() => { throw new NullReferenceException("Test exc in UI thread"); });
task.Start();
}
Please, advise.

Answer 1

Using the UnobservedTaskException event of TaskScheduler you can catch all exceptions in Tasks that are not awaited. Just to clarify: If you await tasks exceptions are propagated to the UI thread and can hence be catched via Application.UnhandledException.

Answer 2

Using the new async/await keywords:
private async void Button_Click_1(object sender, RoutedEventArgs e)
{
var task = new Task(() => { throw new NullReferenceException("Test exc in UI thread"); });
task.Start();
try
{
await task;
}
catch (Exception ex)
{
var msg = new MessageDialog(ex.ToString(), "An error has occurred");
await msg.ShowAsync();
}
}
Using just the Task methods:
private void Button_Click_1(object sender, RoutedEventArgs e)
{
var task = new Task(() => { throw new NullReferenceException("Test exc in UI thread"); });
task.ContinueWith(t =>
{
var msg = new MessageDialog(t.Exception.ToString(), "An error has occurred");
msg.ShowAsync().Start();
}, TaskContinuationOptions.OnlyOnFaulted);
task.Start();
}
For catching all unhandled exceptions, see this question:
How do I add a Global Exception handler to a Metro Style App?