Hierarchical data is usually used to display data in a tree. The data typically is in a single table that is self-referencing, meaning it has one property that points to other records in the same table. This is how it is able to track the parent-child relationship between records. A Tree Control is usually used to visualize hierarchical data.
Karol Zadora-Przylecki (Microsoft) created an example, and included important code required by LightSwitch when using a Silverlight Tree Control. You can see the original post here: http://social.msdn.microsoft.com/Forums/en-US/lsextensibility/thread/bcdaa86f-459a-47d3-853a-3c5e56eb088a. In this article, we will follow the concepts outlined by that post.
Note: If you are new to LightSwitch, it is suggested that you start here: Online Ordering System (An End-To-End LightSwitch Example)