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The OnClientNodeDropping client-side event is called before nodes are dropped and can be canceled.

The event handler receives parameters:

  1. The TreeView instance that fired the event.

  2. Event arguments with functions:

  • get_destNode() retrieves a reference to the destination node, i.e. the node that is being dropped onto.

  • get_dropPosition() returns the relative position of the dropped node(s) and can be "over", "above" or "below".

  • get_htmlElement() retrieves the DOM html element representing the destination node.

  • get_sourceNode() retrieves the node being dropped.

  • get_sourceNodes() retrieves an array of nodes being dropped. It is useful when the RadTreeView MultipleSelect property is True.

  • 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 dropping.

The example below demonstrates preventing a node from being dropped between levels and also displays information from each of the eventArgs functions.

        <telerik:RadTreeView RenderMode="Lightweight" ID="RadTreeView1" 
function ClientNodeDropping(sender, eventArgs) {
    if (eventArgs.get_sourceNode().get_level() != eventArgs.get_destNode().get_level()) {
        alert("You cannot drag nodes between levels");
    else {
        alert("The source node is: " + eventArgs.get_sourceNode().get_text() + "\n" +
        //if MultipleSelect = True
       "The number of source nodes: " + eventArgs.get_sourceNodes().length + "\n" +
       "The destination node is: " + eventArgs.get_destNode().get_text() + "\n" +
       "The HTML element is: " + eventArgs.get_htmlElement().innerHTML + "\n" +
       "The drop position is: " + eventArgs.get_dropPosition()