Silverlight Guidance - How to do this from Telerik? (reference attached image)

I really like a certain Silverlight feature that I've seen in a couple of sites. I would like to know what this "concept(s)" is/are so I can do more research and implemented it on my own. If you see the attached image, I like those expandable sections, reference (1) and (2) sections. They are circled in red and the features that I开发者_Go百科 like are green and expandable.

For a live demo: http://demos.telerik.com/silverlight/#DataPager/FirstLook

Thanks for any advice.

Judging by the screenshot, it's just a collapsible pane. Such a control would have an API allowing two pieces of child content to be supplied, an orientation to be set (horizontal/vertical), and perhaps a collapse direction (left/right or up/down).

The control's template would place each piece of content alongside the other with a separator in between. Clicking the separator would collapse one piece of content in the chosen direction, thus giving the other piece of content more room.