I'm trying to create a reflection effect and it's working great except that I have to hard-code some values. This is my XAML:

 <Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="60"/>
        <RowDefinition />
        <RowDefinition Height="80"/>
    </Grid.RowDefinitions>
    <StackPanel Grid.Row="1" VerticalAlignment="Center">
        <UserControl x:Name="CurrentPresenter" />
        <Border Width="500" Height="200" >
            <Border.Background>
                <VisualBrush Visual="{Binding ElementName=CurrentPresenter}" >
                    <VisualBrush.Transform>
                        <TransformGroup>
                            <ScaleTransform ScaleX="1" ScaleY="-1" CenterX="500" CenterY="99" />
                        </TransformGroup>
                    </VisualBrush.Transform>
                </VisualBrush>
            </Border.Background>
            <Border.OpacityMask>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="0,0.6">
                        <GradientStop Offset="-0.6" Color="Black"></GradientStop>
                        <GradientStop Offset="0.6" Color="Transparent"></GradientStop>
                    </LinearGradientBrush>
                </Border.OpacityMask>
        </Border>
    </StackPanel>
</Grid>

I've tried to replace Border's Width="500" and Height="200" by Width="{Binding ElementName=CurrentPresenter, Path=Width}" and Height="{Binding ElementName=CurrentPresenter, Path=Height}" but it doesn't seem to work.

Wha's wrong with this code?

UPDATE: If I set Width and Height here:

<UserControl x:Name="CurrentPresenter" Height="200" Width="500" />

It works as expected. However it doesn't work if I set those values in the UserControl XAML. Any ideas?