Windows Phone UnautorizedAccessExeption when using Task

Question

I try using Task object to run code asynchronously:

public void buttonAnswer_Click(object sender, RoutedEventArgs e)
    {
        Task t = new Task(() =>
        {
            System.Threading.Thread.Sleep(1000);
            MessageBox.Show("Test..");
        });

        t.Start();
    }

But when run application on device i get UnautorizedAccessExeption exeption on MessageBox.Show("Test.."); line.

visual studio screenshot

Answer 1

You can't access the user interface elements in background thread. You should marshal the call to the UI thread instead.

Using async/await it's fairly simple thing to do.

public async void buttonAnswer_Click(object sender, RoutedEventArgs e)
{
    await Task.Run(() =>
    {
        //Your heavy processing here. Runs in threadpool thread
    });
    MessageBox.Show("Test..");//This runs in UI thread.
}

If you can't use async/await, you can use Dispatcher.Invoke/Dispatcher.BeginInvoke methods to execute the code in UI thread.