Animate a StackPanel when the property Visibility changes

Question

In WPF 3.5 (with SP1), I have simply StackPanel that I would like to animate when I change the property Visibility. I have no idea of the height of this StackPanel since its content determines its height. So when I change the property of my StackPanel to Visible (progressPanel.Visibility = Visibility.Visible;) I would like to see an animation (probably an DoubleAnimationUsingKeyFrames from 0 to X).

Moreover, I have multiple StackPanel that I would like to see with this behavior (so in the best case, I need something generic). Does anybody have an idea on how to do that?

Thanks!

Answer 1

If you need an expanding kind of effect with an animation which grows vertically. Do a double animation on the ScaleTransform.ScaleY property of the panel from 0 to 1 if it is a vertical oriented panel.

Answer 2

You can create and reuse custom StackPanel style that triggers animation when Visibility changes:

<Style x:Key="MyStyle" TargetType="{x:Type StackPanel}">
    <Style.Triggers>
        <Trigger Property="Visibility" Value="Visible">
            <Trigger.EnterActions>
                <BeginStoryboard>
                    <Storyboard >
                        <DoubleAnimation .../>
                    </Storyboard>
                </BeginStoryboard>
            </Trigger.EnterActions>
        </Trigger>
    </Style.Triggers>
</Style>

Answer 3

Did you ever solidify a solution; would you mind posting the XAML if you did.

Thanks! Aj

Answer 4

The Reveal control from Kevin's Bag-o-Tricks ( http://j832.com/bagotricks/ ) does exactly that.

Answer 5

Adding rendertransform on stackpanel does not seem to do the trick for me as my stackpanel is withing a GRID that has some rectangles as well, and the stackpanel width is dynamically set by the contents I put in it. I tried: Visible Collapsed

But this does not really "animate" It just waits 4 sec and immediately closes "collapses" the stackpanel... I want it to close slllooooowwwwly (like in 4 secs)...

Any HELP posting would help us all! thanks, Anastasia