Why does an event handler output all of its actions at the same time?

Question

I want that when the button is pressed, two numbers one are displayed with an interval of half a second in textbox

But if you do everything as in my example, both numbers are displayed simultaneously in half a second

  private void Button_Click(object sender, RoutedEventArgs e)
        {
            Checker.Text += "1";

            System.Threading.Thread.Sleep(500);

            Checker.Text += "1";
        }

The same will happen with any loop inside any event handler

score 0 · Accepted Answer · answered Jul 13 '21 at 15:40

The Thread.Sleep() call will block the Dispatcher thread. Its that thread that updates your UI, in order to do what you want you will need to either run a background worker thread, or more simply use the Async/Await syntax

  private async void Button_Click(object sender, RoutedEventArgs e)
    {
        Checker.Text += "1";

        await Task.Delay(500);

        Checker.Text += "1";
    }

Why does an event handler output all of its actions at the same time?

1 Answers1