The following article demonstrates how to use and subscribe to the OnClientNodeExpanding client-side event of the RadNavigation control.

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The client-side OnClientNodeExpanding event of the RadNavigation is raised when some Node is about be expanded. The expand of some node could appear when the mouse is moved on the node. In scenario when the ClickToOpen property of the RadNavigation is set to true, the expand will be fired when the node is clicked.

To handle this event, simply write a JavaScript function that can be called when the event occurs. Then assign the name of this function as the value of the OnClientNodeExpanding property. This event could be canceled and the technique for achieving this is demonstrated in Example 1.

The client-side OnClientNodeExpanding event handler receives two arguments:

  • Sender — the RadNavigation object that fired the event.

  • Event arguments — an event arguments object that exposes the following methods:

ButtonClicking Event Arguments Object

Name Parameters Return Type Description
get_cancel() bool Gets a value that indicates whether the event is canceled.
set_cancel(value) bool Sets whether the event will be canceled (if true is passed).
get_node() Telerik.Web.UI.NavigationNode Returns an instance of NavigationNode that is about to be expanded.

Example 1: Handle the RadNavigation's client-sideOnClientNodeExpanding event in order to cancel its propagation.

<script type="text/javascript">
    function OnClientNodeExpanding(sender, eventArgs) {
        var expandNodeText = eventArgs.get_node().get_text();

        if (expandNodeText == "Node1")

<telerik:RadNavigation runat="server" ID="RadNavigation1" OnClientNodeExpanding="OnClientNodeExpanding">
        <telerik:NavigationNode Text="Node1">
                <telerik:NavigationNode Text="ChildNode1"></telerik:NavigationNode>
                <telerik:NavigationNode Text="ChildNode2"></telerik:NavigationNode>
                <telerik:NavigationNode Text="ChildNode3"></telerik:NavigationNode>
                <telerik:NavigationNode Text="ChildNode4"></telerik:NavigationNode>
        <telerik:NavigationNode Text="Node2"></telerik:NavigationNode>
        <telerik:NavigationNode Text="Node3"></telerik:NavigationNode>
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