OnSelectedIndexChanging

Updated on Aug 24, 2026

The selectedIndexChanging event occurs when users changes the checked state of an item in RadCheckBoxList. This event can be canceled.

The event handler receives two parameters:

1. The instance of the loaded RadCheckBoxList control.

2. An eventArgs parameter of type Telerik.Web.UI.ButtonListCancelEventArgs, containing the following properties and methods:

   • get_item() - returns an instance of type Telerik.Web.UI.ButtonListItem (the clicked item).
   • get_cancel() - sets a bool value that indicates whether the event will be canceled. Setting true means the event will be canceled.
   • set_cancel() - returns a bool value that indicates whether the event was canceled. True means the event is canceled.

Example 1: Handling RadCheckBoxList OnSelectedIndexChanging event.

ASP.NET

<script type="text/javascript">
	function OnSelectedIndexChanging(sender, args) {
		var selectedLanguage = args.get_item().get_text();
		var toChange = !confirm("You are about to change to " + selectedLanguage + " language!");
		args.set_cancel(toChange);
	}
</script>

<telerik:RadCheckBoxList runat="server" ID="RadCheckBoxList1">
	<ClientEvents OnSelectedIndexChanging="OnSelectedIndexChanging" />
	<Items>
		<telerik:ButtonListItem Text="English" Selected="true" />
		<telerik:ButtonListItem Text="German" />
		<telerik:ButtonListItem Text="French" />
	</Items>
</telerik:RadCheckBoxList>

See Also

• CheckBoxList Object

• Events Overview

• OnLoad (load)

• OnItemLoad (itemLoad)

• OnItemClicking (itemClicking)

• OnItemClicked (itemClicked)

• OnSelectedIndexChanged (selectedIndexChanged)

• OnItemMouseOver (itemMouseOver)

• OnItemMouseOut (itemMouseOut)