# OnClientNodePopulationFailed

The **OnClientNodePopulationFailed** client-side event occurs when:

* Child nodes are loaded on-demand.

* The parent node **ExpandMode** property is **ServerSideCallback** or **WebService**.

* An exception occurs while loading.

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 parent node.

* **get_errorMessage()** retrieves the exception message text.

* **set_cancel()** - call this function to specify whether the event should be canceled (true) or not (false). Canceling of the event will prevent the exception from propagating.

* **get_domEvent()** retrieves a DOM event object.

In the example below an exception is raised in the server-side [NodeExpand](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/server-side-programming/events/nodeexpand) event handler

```ASPNET
<telerik:RadTreeView RenderMode="Lightweight" ID="RadTreeView1" runat="server" OnClientNodePopulationFailed="ClientNodePopulationFailed"
    OnNodeExpand="RadTreeView1_NodeExpand">
    <Nodes>
        <telerik:RadTreeNode runat="server" ExpandMode="ClientSide" Text="Search" ImageUrl="~/images/search.ico"
            Expanded="True" Value="1">
            <Nodes>
                <telerik:RadTreeNode runat="server" ExpandMode="ServerSideCallBack" Text="Recent Searches">
                </telerik:RadTreeNode>
                <telerik:RadTreeNode runat="server" ExpandMode="ServerSideCallBack" Text="Network Locations">
                </telerik:RadTreeNode>
            </Nodes>
        </telerik:RadTreeNode>
    </Nodes>
</telerik:RadTreeView>
```

```JavaScript
function ClientNodePopulationFailed(sender, eventArgs) {

	var node = eventArgs.get_node();
	var message = eventArgs.get_errorMessage();
	
	alert("OnClientNodePopulationFailed fired for node " +
		node.get_text() +
		" with message[" +
		message + "]");
		
	eventArgs.set_cancel(true);
}
```

> caution Note that the custom alert will appear on remote clients, only if the **customErrors** mode is set to **Off** in the web.config:
> <customErrors mode="Off"></customErrors>

The server **NodeExpand** event handler for the **RadTreeView** defined above:

```C#
protected void RadTreeView1_NodeExpand(object sender, Telerik.Web.UI.RadTreeNodeEventArgs e)
{    
    throw new ApplicationException("An error occurred while attempting to populate " + e.Node.Text);
}
```

```VB.NET
Protected Sub RadTreeView1_NodeExpand(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadTreeNodeEventArgs)
    Throw New ApplicationException("An error occurred while attempting to populate " + e.Node.Text)
End Sub
```

## See Also

* [OnClientNodePopulating](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodepopulating)

* [OnClientNodePopulated](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/events/onclientnodepopulated)

* [RadTreeNode](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/client-side-programming/objects/radtreenode)