How can I use the attached properties of Canvas to position child elements ?

This example shows how to use the attached properties of Canvas to position child elements.

[XAML]

<Page xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation' WindowTitle='Canvas Attached Properties Sample'>
  <Border HorizontalAlignment='Left' VerticalAlignment='Top' BorderBrush='Black' BorderThickness='2'>
    <Canvas Background='LightBlue' Width='400' Height='400'>
      <Button Canvas.Top='50'>Canvas.Top='50'</Button>
      <Button Canvas.Bottom='50'>Canvas.Bottom='50'</Button>
      <Button Canvas.Left='50'>Canvas.Left='50'</Button>
      <Button Canvas.Right='50'>Canvas.Right='50'</Button>
    </Canvas>
  </Border>    
</Page>