# OnClientNodeDropping

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.

```ASPNET
	    <telerik:RadTreeView RenderMode="Lightweight" ID="RadTreeView1" 
	                         runat="server" 
	                         EnableDragAndDrop="True" 
	                         MultipleSelect="True"
	                         OnClientNodeDropping="ClientNodeDropping">
	    </telerik:RadTreeView>
```

```JavaScript
function ClientNodeDropping(sender, eventArgs) {
    if (eventArgs.get_sourceNode().get_level() != eventArgs.get_destNode().get_level()) {
        alert("You cannot drag nodes between levels");
        eventArgs.set_cancel(true);
    }
    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()
        );
    }
}
```