How to use OpacityMask to make UIElement partly invisible

<Button HorizontalAlignment=”Stretch” VerticalAlignment=”Stretch” Content=”Button”>
<Button.OpacityMask>
<LinearGradientBrush EndPoint=”0.5,1″ StartPoint=”0.5,0″>
<GradientStop Color=”#FF000000″ Offset=”0″/>
<GradientStop Color=”#FF000000″ Offset=”0.5″/>
<GradientStop Color=”#00000000″ Offset=”0.5″/>
</LinearGradientBrush>
</Button.OpacityMask>
</Button>

~ by Martin on December 16, 2008.