Windows Phone 綁定滑動的控件的值來進行相應的設置

   <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
            <Grid.RowDefinitions>
                <RowDefinition Height="auto"/>
                <RowDefinition Height="auto"/>
            </Grid.RowDefinitions>
            <Rectangle Margin="25,5,0,25" Width="245" Height="150" Fill="Yellow" Grid.Row="0" Opacity="{Binding Path=Value, ElementName=a}"/>
            <Slider Name="a" Grid.Row="1" Maximum="1" Minimum="0" SmallChange="0.001"/>
        </Grid>