WPF Popup event handling - How to get triggered when Popup opens

Question

I created a WPF Popup which contains a grid with border. There is some animation associated with the border which I want to be triggered every time the Popup opens.

Currently the code is like this

<Popup x:Name="myPopUp" >
  <Border x:Name="myBorder" >
    <Border.Triggers>
               <EventTrigger RoutedEvent="Popup.Loaded">
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation
                                    Storyboard.TargetName="myBorder" 
                                    Storyboard.TargetProperty="Height"
                                    From="10" To="255" Duration="0:0:0.20" />                      
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
     </Border.Triggers>
     <Grid />
   </Border>
</Popup>

As per the code the border shows up the animation for the first time the popup opens. What change do I need to make to trigger the border animation every time the Popup opens?

Answer 1

As per suggestions given here and a little bit expireince now (I asked this a year back :) ), I could figure out the solution.

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525" >
<Window.Resources>
    <Style x:Key="popupStyle" TargetType="{x:Type Popup}" >
        <Style.Triggers>
            <Trigger Property="IsOpen" Value="True">
                <Trigger.EnterActions>
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation
                                Storyboard.TargetProperty="Height"
                                From="10" To="255" Duration="0:0:0.20" />
                        </Storyboard>
                    </BeginStoryboard>
                </Trigger.EnterActions>
            </Trigger>
        </Style.Triggers>
    </Style>
</Window.Resources>
<Grid>
    <Button Width="100" Height="100" Click="Button_Click"></Button>
    <Popup Name="popUp" Width="100" Height="100"  Style="{StaticResource popupStyle}" >
        <Border x:Name="myBorder" Background="Blue"/>
    </Popup>
</Grid>

and a sample code behind to trigger the popup..

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        popUp.PlacementTarget = (Button)sender;
        popUp.IsOpen = true;
    }

Although I can only animate the Popup and not the Border here, it pretty much gives the same result.

Answer 2

I'm not sure if the popup gets focus when it opens, but you could use the GotFocus event if it does. Alternatively, you could try using a datatrigger on the is IsOpen property. I think you'd have to put that in a style though instead of inline.