<Window x:Class="AnimationBindingTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:app="clr-namespace:AnimationBindingTest"
        Title="MainWindow" Height="350" Width="525">
    <Grid x:Name="OuterGrid">
        <StackPanel x:Name="ContractSelect_Panel" Width="100" Height="30" Opacity="0.2" Background="Green">
            <StackPanel.Resources>
                <Storyboard x:Key="ShowModal">
                    <DoubleAnimation Storyboard.TargetName="ContractSelect_Panel"
                             Storyboard.TargetProperty="Opacity"
                             To="1" Duration="0:0:0.15"/>

                    <DoubleAnimation Storyboard.TargetName="ContractSelect_Panel"
                             Storyboard.TargetProperty="Width"
                             To="264" Duration="0:0:0.15"/>

                    <DoubleAnimation Storyboard.TargetName="ContractSelect_Panel"
                             Storyboard.TargetProperty="Height"
                             To="{Binding ActualHeight, ElementName=OuterGrid}" Duration="0:0:0.15"/>
                </Storyboard>
            </StackPanel.Resources>
            <StackPanel.Triggers>
                <EventTrigger RoutedEvent="MouseUp">
                    <BeginStoryboard Storyboard="{StaticResource ShowModal}"/>
                </EventTrigger>
            </StackPanel.Triggers>
        </StackPanel>
    </Grid>
</Window>