I built a feature to have an animation on the wide of a panel and the user click the minimize button. I wish to create a shrinking effect.
The best way I found is using DoubleAnimationUsingKeyFrames. This kind of animation can targeting any properties which is using a double as its value, such as Wide. Finally, I put the into a storyboard. Like the following

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The example is from my opensource project, advgen contact manager

In Winform, to show and hide button is easy. There is a property calls visible in Button class. You just need to set it to be True and Hide. That is a simple bool type. In WPF, that is simple too, but that is not a simple bool type. That is Visibility Type.
You just need to do that:
Show:

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Source:Open Clip Art Using Under Public Domain Attribution
I got a control in style template at one of my custom controls, Like this:
<Style TargetType="{x:Type advgenControls:CollapsibleControl}" x:Key="LeftPanel">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type advgenControls:CollapsibleControl}">
<Grid>

<ContentPresenter x:Name="PART_ContentPresenter"/>
<ResizeGrip Grid.Row="1" HorizontalAlignment="Stretch" Width="Auto" Height="Auto" HorizontalContentAlignment="Right" Margin="0,0,2,2"/>
</Grid>


</ControlTemplate>
</Setter.Value>
</Setter>

</Style>

I just want to call that "PART_ContentPresenter". But that is xaml living in resources.
That is easy I can use GetTemplateChild("PART_ContentPresenter" ) and call at the OnApplyTemplate(). Please remember don't use it at OnInitialized(EventArgs e). At that time, styles has not loaded yet, you get a null object.:

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Source:Open Clip Art Using Under Public Domain Attribution
I found the wpf user control cannot have any child has a name attribute, such as:

    <advgenControls:CollapsibleControl>            <TreeView 
                x:Name="treeView"     Style="{StaticResource MainLeftPanel}" /></advgenControls:CollapsibleControl> 

It will have the error like this:
Cannot set Name attribute value 'treeView' on element 'TreeView'. 'TreeView' is under the scope of element 'CollapsibleControl', which already had a name registered when it was defined in another scope. Line 93 Position 5. (MC3093) - D:\Projects\AdvGenContact\AdvGenContact\AdvGenContact.WPF\MainWindow.xaml:93,5

I did a research on internet, I even tried some suggestions in internet, it doesn't work at all. I found that is no way to do that. I believe that is because User Control is not for that purpose. The user control is to hold some repeatable content across the applications. For example, I got a status bar which it need to place all every window in my application. Then I should create a user control for my own status bar and place into every window. In my case mentioned above, I wish to build a collapsible panel which has a different content in each window, even I will reuse that in other project. User Control is not my best. I should find an existing control to override. In this case, I should use HeaderItemsControl.

Note that: when I finish this control, I will put on my open source probject, AdvGen Contact Manager.

Stackpanel is a useful layout control in WPF. If you have a set of elements need to sit side by side each other, this is your best option. For example, in my advgen contact manager, in the right hand side, there is a set of buttons. Thus, I placed a stack panel. However, by the default, the controls inside the panel will flow in vertical direct, you need to set Orientation="Horizontal"
E.g.
<StackPanel FlowDirection="LeftToRight" Orientation="Horizontal">