TreePanel inherits from TablePanel, which is also the abstract parent class of GridPanel. This means that trees can get many features that GridPanels do (for example, multiple columns). A TreePanel can also work with a subclass of Store—the TreeStore—which is especially useful for AJAX-based tree interactions. These useful architectural changes from previous versions of Ext.NET increase familiarity and code reuse, while making TreePanels quite rich.
We will leave the Store aspect for a later part of this chapter. In this section we will have a look at the basic mechanics of putting a TreePanel together.
A TreePanel is made up of nodes. A node may have children, which are more nodes. If a node does not have any child nodes it is referred to as a leaf node. A TreePanel has a single root node (which is optional to display). Tree nodes can be loaded upfront when the page is loaded (or when the TreePanel is constructed), or nodes can be expanded and populated locally...