C# WPF key held

I have a problem with key held. Everything works when it's just key down but what about key holding? The code looks like this:

private void Window_KeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Up || e.Key == Key.Down)
    {
       moveBall(3);
    }
}

Thanks for replies.