ListView with 2 Labels: One left andone right

Hi,
I have a ListView with two labels on each row. One should be at the left and the other on the right. Why doesn't this code work? It shows the two labels aligned to the left.

<StackLayout Padding="15,10,15,10"  Orientation="Horizontal" >
    <Label Text="{Binding Title}" YAlign="Center" FontSize="Medium" />
    <Label Text="{Binding Value}" YAlign="Center" XAlign="End" FontSize="Medium" FontAttributes="Bold"/>
</StackLayout>