Animation
By default the RadTreeView control's items are expanded and collapsed with an animation. The expand\collapse animations are represented by a TreeViewExpandCollapseAnimation object. This class derives from RadAnimation. The animation direction is controlled by the AnimationType property of the TreeViewExpandCollapseAnimation class. So if you want to change the speed of the expand\collapse you can use the AnimationManager.AnimationSelector attached property.
Change Animation Speed
Example 1: Change animation speed
<telerik:RadTreeView xmlns:animationNavigation="clr-namespace:Telerik.Windows.Controls.Animation;assembly=Telerik.Windows.Controls.Navigation" >
<telerik:AnimationManager.AnimationSelector>
<telerik:AnimationSelector>
<animationNavigation:TreeViewExpandCollapseAnimation AnimationName="Expand"
Direction="In" SpeedRatio="0.25" />
<animationNavigation:TreeViewExpandCollapseAnimation AnimationName="Collapse"
Direction="Out" SpeedRatio="0.25" />
</telerik:AnimationSelector>
</telerik:AnimationManager.AnimationSelector>
</telerik:RadTreeView>
Disable Default Animation in RadTreeView
When you have a large number of subitems it takes a longer time for the animations to complete. In this case you can consider disabling the animation to speed up the expand\collapse performance. To disable the default animations, all you have to do is to set the following attached property to the RadTreeView control:
Example 1: Disable expand\collapse animation
<telerik:RadTreeView telerik:AnimationManager.IsAnimationEnabled="False"/>