An enhancement has been made that allows you to add animation when items are added ,or removed from, the list box. Silverlight 4 adds a new StateGroup to the ListBoxItem class:
A Simple Demo
The user types into the text box, clicks the add button and the text “floats” up into the list.
So Where Is the Magic??
To take advantage of the new FluidUI all you need to do is to set the behavior you want on any or all of the three new Visual States in the LayoutStates group of the ListBoxItem class.
The easiest way to do this is to open the project in Blend and right click on the ListBox. Choose Edit Additional Templates –> Edit Generated Item Container –> Edit a Copy
To do so, click on the Loaded state and then expand the timeline. You’ll set new values for the entire Grid (which has 4 sub-elements).
select 0 seconds, and set the opacity to 0 and the y coordinate of a translate-transform to 200. Click save keyframe values, and then select 1 second and set the opacity to 1 and the y coordinate to 0. Save the new template…