Hwo to design this site menu style in WPF : I do not speak English well. So, I used Google translator. Sorry...

I am trying to implement www.devexpress.com menu.
But I do not know what to do to implement the unfolding details below.

this is my source file.
[enter link description here][1]


  [1]: https://drive.google.com/open?id=0B2twYdJfAGHHYXUtU0I4YVdRak0

thank you.