# Events Overview

**RadTreeView** supports a number of client-side events that let you customize behavior:

* [OnClientContextMenuItemClicked](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientcontextmenuitemclicked): occurs when the user clicks a context menu item for a node.

* [OnClientContextMenuItemClicking](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientcontextmenuitemclicking): occurs when the user clicks a context menu item for a node but before the OnClientContextMenuItemClicked event.

* [OnClientContextMenuShowing](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientcontextmenushowing): occurs just before the context menu is displayed.

* [OnClientContextMenuShown](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientcontextmenushown): occurs when the context menu is displayed.

* [OnClientDoubleClick](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientdoubleclick): occurs when a node is double-clicked with the mouse.

* [OnClientKeyPressing](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientkeypressing): occurs when any key is pressed while the **TreeView** is having the focus.

* [OnClientMouseOut](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientmouseout): occurs when the mouse leaves the area of a node.

* [OnClientMouseOver](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientmouseover): occurs as the mouse passes over a node.

* [OnClientNodeChecked](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodechecked): occurs after a node checkbox value is toggled.

* [OnClientNodeChecking](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodechecking): occurs when just before the checkbox value is toggled.

* [OnClientNodeClicked](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeclicked): occurs when a node is navigated to by the mouse or keyboard.

* [OnClientNodeClicking](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeclicking): occurs when a node is navigated to by the mouse or keyboard and before the OnClientNodeClicked event.

* [OnClientNodeCollapsed](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodecollapsed): occurs when a parent node collapses to hide its child nodes.

* [OnClientNodeCollapsing](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodecollapsing): occurs just before a parent node collapses to hide its child nodes.

* [OnClientNodeDataBound](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodedatabound): occurs when a Node is being created during Web Service Load on Demand.

* [OnClientTemplateDataBound](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclienttemplatedatabound): occurs after the client template is being bound against the DataItem.

* [OnClientNodeDragging](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodedragging): occurs while a node is being dragged.

* [OnClientNodeDragStart](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodedragstart): occurs as the drag operation begins.

* [OnClientNodeDropped](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodedropped): occurs when a node is dropped on another node, between nodes or on an HTML element.

* [OnClientNodeDropping](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodedropping): occurs just before a node is dropped.

* [OnClientNodeEditStart](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeeditstart): occurs as the edit begins.

* [OnClientNodeEdited](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeedited): occurs when a node has been edited by the end user.

* [OnClientNodeEditing](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeediting): occurs after the user has finished editing but before the **OnClientNodeEdited** event.

* [OnClientNodeExpanded](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeexpanded): occurs after a parent node has expanded to display its child nodes.

* [OnClientNodeExpanding](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeexpanding): occurs just before a parent node expands to display its child nodes.

* [OnClientNodePopulated](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodepopulated): occurs when a load-on-demand operation has populated the child nodes of a parent node.

* [OnClientNodePopulating](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodepopulating): occurs just before a load-on-demand operation has populated the child nodes of a parent node.

* [OnClientNodePopulationFailed](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodepopulationfailed): occurs when an error occurs on the server in a load-on-demand operation.

* [OnClientLoad](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientload): occurs after the **RadTreeView** client-side object has been fully initialized.

* [OnClientNodeAnimationEnd](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodeanimationend): occurs when the node is expanded / collapsed and after the animation has finished

To use these events, write a javascript function that can be called when an event occurs. Then assign the name of the JavaScript function as the value of the corresponding **RadTreeView** event property.

```ASPNET
<telerik:RadTreeView RenderMode="Lightweight" 
    ID="RadTreeView1" 
    runat="server"  
    OnClientNodeClicked="ClientNodeClicked">
</telerik:RadTreeView>
```

```JavaScript
function ClientNodeClicked(sender, eventArgs) 
{
	var node = eventArgs.get_node();
	alert("You clicked " + node.get_text());
}
```

You can also assign event handlers in client-side code:

```JavaScript
function AssignEventHandler()
{
	var tree = $find("<%= RadTreeView1.ClientID %>");
	tree.add_nodeClicked(ClientNodeClicked);
}	
```

Another advantage of the client-side API is that you can detach an event handler dynamically:

```JavaScript
function removeOnClicked2()
{
	var tree = $find("<%= RadTreeView1.ClientID %>");
	tree.remove_nodeClicked(ClientNodeClicked);
}	
```

For a live example of using client-side events, see [Client-Side Events Demo](https://demos.telerik.com/aspnet-ajax/TreeView/Examples/Programming/ClientEvents/DefaultCS.aspx).