How to bind RadTreeView to hierarchical data and use load-on-demand

How to bind RadTreeView to hierarchical data and use load-on-demand?

1. This article is based on the approach described in the Populating Silverlight TreeView from WCF Service with LINQ to SQL article. Therefore, before going further make sure you’ve read and understood it, so that you have the necessary background.

2. Now that we have the basis set up it’s time to go on. First we need to add an event handler for the Expanded event:

3. Then we need to switch to the code-behind and add the code to handle the event:

Here we first get references to the treeview and the item that was expanded. Then, we get a reference to the hierarchical data source and call its LoadItemChildren method and pass it the value of the expanded item. What the method does is fetch the children of that data item via the web service and add them as children of the treeview.

4. Next, we will add the LoadItemChildren() method to the HierarchicalDataSource.cs file.


The method visits all current items and adds their direct children to the data source, if there are any.

5. After that we have to modify the FindChildren() method by removing the iterative call:

This way when the tree is displayed for the first time the root node will have only the first level of items loaded.

6. That’s it – you now have a treeview bound to a collection of custom objects which are loaded on demand.

Attached, please find a sample project demonstrating the above approach.

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