Animation
By default the RadPanelBar control's items are expanded and collapsed without an animation. To enable the expand\collapse animations you can use the telerik:AnimationManager.IsAnimationEnabled attached property. To customize the animation you could use the PanelBarExpandCollapseAnimation object.
Enable Animation in RadPanelBar
The animation is enabled by setting the telerik:AnimationManager.IsAnimationEnabled property to True.
[XAML] Example 1: Enable expand\collapse animation
<telerik:RadPanelBar telerik:AnimationManager.IsAnimationEnabled="True">
Change Animation Direction
The animation direction is controlled by the Direction property of the PanelBarExpandCollapseAnimation class and it is either In or Out.
[XAML] Example 2: Set expand\collapse directions
<telerik:RadPanelBar xmlns:animationNavigation="clr-namespace:Telerik.Windows.Controls.Animation;assembly=Telerik.Windows.Controls.Navigation">
<telerik:AnimationManager.AnimationSelector>
<telerik:AnimationSelector>
<animationNavigation:PanelBarExpandCollapseAnimation AnimationName="Expand" Direction="In"/>
<animationNavigation:PanelBarExpandCollapseAnimation AnimationName="Collapse" Direction="Out"/>
</telerik:AnimationSelector>
</telerik:AnimationManager.AnimationSelector>
</telerik:RadPanelBar>
Change Animation Speed
The speed of the expand\collapse is also customizable via the AnimationManager.AnimationSelector attached property.
[XAML] Example 3: Change animation speed
<telerik:RadPanelBar xmlns:animationNavigation="clr-namespace:Telerik.Windows.Controls.Animation;assembly=Telerik.Windows.Controls.Navigation">
<telerik:AnimationManager.AnimationSelector>
<telerik:AnimationSelector>
<animationNavigation:PanelBarExpandCollapseAnimation AnimationName="Expand" Direction="In" SpeedRatio="0.25"/>
<animationNavigation:PanelBarExpandCollapseAnimation AnimationName="Collapse" Direction="Out" SpeedRatio="0.25"/>
</telerik:AnimationSelector>
</telerik:AnimationManager.AnimationSelector>
</telerik:RadPanelBar>
The SpeedRatio property controls the duration. A value of 0.25 means that the animation will play a quarter (25%) of the default animation duration (for example, 15 of 60 seconds). A value of 1, means that the default time will be used. A value of 1.33 means that the animation will be played 33% faster than the default time.