In many cases, you'll want to avoid rendering your TreeView Control with a full dataset. Rather, you'll want to load all visible nodes immediately and then retrieve data only when needed for nodes that aren't visible when the control is first loaded. This example shows you how to do that.
In the TreeView instance below, we've loaded all "top-level" nodes into the page as soon as the page loads; these nodes contain the names of many Indian states. When a node is expanded, we use Connection Manager to access a Yahoo! Search web service that will return a list of "related suggestions." So when the page loads, we know nothing about our top-level nodes' children. And while the resulting TreeView instance could grow quite large through user interaction, we need only load a very light set of nodes to begin with.
This example also shows the two label styles for childless nodes. The first (default) style maintains the expand/collapse icon style even when the node has no children; the second style shows childless nodes as leaf nodes with no expand/collapse icon. Note: this is for dynamically loaded nodes after the dynamic load process has produced zero children. You can also force the leaf node presentation for any node by setting the isLeaf property to true (this also disables dynamic loading).