ASP.NET 4 Unleashed

Using Populate On Demand and AJAX

You can use the TreeView control even when working with a large set of data. For example, the Microsoft MSDN website (msdn.Microsoft.com) has links to thousands of articles. This website uses a tree view to display the nested links to the articles.

Because thousands of articles are hosted at the MSDN website, not all the tree nodes are downloaded to the browser when you open a page. Instead, additional nodes are downloaded to your browser only when you expand a particular node.

You can use a feature named Populate On Demand with the TreeView control. When you enable the PopulateOnDemand property for a Tree node, child nodes are not added to the parent node until the parent node is expanded.

For example, the page ...