If you need to expand a specific node of the RadTreeView control here is a very good help article that explains how this could be achieved on the server.:Tutorial: Finding Nodes. However, if you need to expand nodes on the client-side you can refer here for more detailed explanation how it could be done (first article is for single node and the second for the collection of nodes - in the middle of the topic you can find an example how to loop through the node collection):
Further, if you choose the client-side approach I would recommend that you use the
OnClientLoad event and assign an event handled as described here.
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