Access to children from StackPanel

Question

Unfortunately I can't find a way to access the children of a StackPanel directly (without creating a parallel list).
E.g. here as a demo to change the background color of a border via index.

Border border;

        private void Button0_Click(object sender, RoutedEventArgs e)
        {
            border = new Border();
            border.Background = new SolidColorBrush(Colors.Red);
            _stack0.Children.Add(border);
            border.Width = 100;
            border.Height = 100;

            border = new Border();
            border.Background = new SolidColorBrush(Colors.Yellow);
            _stack0.Children.Add(border);
            border.Width = 75;
            border.Height = 75;

            border = new Border();
            border.Background = new SolidColorBrush(Colors.Green);
            _stack0.Children.Add(border);
            border.Width = 50;
            border.Height = 50;
        }

        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            _stack0.Children[0].Opacity = 0.5;
            //Change Background of Children[0] ???

        }

Answer 1

Try something like this:

private void Button1_Click(object sender, RoutedEventArgs e)
{
   Border b = _stack0.Children[0] as Border;
   if( b != null) 
   {
      b.Background = . . .
   }
}

Answer 2

Super, Thank You!

Answer 3

Super, Thank You!