c# async sleep

// Async
await Task.Delay(1000); //when you want a logical delay without blocking the current thread
// Not Async
Thread.Sleep(1000) //when you want to block the current thread.

private async void Button_Click_1(object sender, RoutedEventArgs e)
{
    label1.Text = "Test";
    await Task.Delay(2000);
    label1.Text = "";
}