New to Telerik UI for ASP.NET AJAX? Download free 30-day trial


The OnClientNodeExpanding client-side event occurs when the user clicks the expand (plus) button. The event is called just prior to postback or URL redirection and can be canceled.

Calling the client-side expand() or set_expanded(true) method does not fire OnClientNodeExpanding and OnClientNodeExpanded client-side events. More information is available here.

The event handler receives parameters:

  1. The TreeView instance that fired the event.

  2. Event arguments with functions:

  • get_node() retrieves a reference to the clicked on node.

  • set_cancel() - call this function to specify whether the event should be canceled (true) or not (false).

  • get_domEvent() retrieves a DOM event object of the node expand.

The example below shows how to prevent expanding a "Recent Searches" node. Note that the OnClientNodeExpanded event does not fire when the expand (plus) button is clicked.

<telerik:RadTreeView RenderMode="Lightweight" ID="RadTreeView1" runat="server" AllowNodeEditing="True" 
function ClientNodeExpanded(sender, eventArgs)
function ClientNodeExpanding(sender, eventArgs)

    var node = eventArgs.get_node();    
    if(node.get_text() == "Recent Searches")

See Also

In this article