# OnColumnHeaderClick

The **OnColumnHeaderClick** client-side event handler of the [ASP NET AJAX Calendar](https://www.telerik.com/products/aspnet-ajax/calendar.aspx) is called when the user is about to select a column of dates by clicking on a column header. The event occurs only if the **ShowColumnHeaders** and **UseColumnHeadersAsSelectors** properties are set to **true**.

The event handler receives two arguments:

1. the [RadCalendar object](https://www.telerik.com/products/aspnet-ajax/documentation/controls/calendar/client-side-programming/radcalendar-object) that fired the event.

2. an event arguments object that exposes the following methods:OnColumnHeaderClick event arguments object

| Name                  | Return Type  | Arguments | Description                                                     |
| --------------------- | ------------ | --------- | --------------------------------------------------------------- |
| **get_index()**       | int          |           | Returns the 1-based index of the column that was clicked.       |
| **get_domElement()**  | HTML element |           | Returns the DOM element for the column header that was clicked. |
| **set_cancel(value)** |              | bool      | Lets you prevent the click from selecting the column of dates.  |

The following example uses the **OnColumnHeaderClick** event to confirm the selection:

```ASPNET
<telerik:RadCalendar RenderMode="Lightweight" ID="RadCalendar1" runat="server">
	<ClientEvents OnColumnHeaderClick="confirmColumnSelection" />
</telerik:RadCalendar>
```

```JavaScript
function confirmColumnSelection(sender, eventArgs) {
	var msg = "Do you want to change the selection for column " + eventArgs.get_index();
	var title = eventArgs.get_domElement().title;

	if (title != "") {
		msg = msg + " (" + title + ")";
	}

	msg = msg + "?";
	eventArgs.set_cancel(!confirm(msg));
}
```

## See Also

* [OnRowHeaderClick](https://www.telerik.com/products/aspnet-ajax/documentation/controls/calendar/client-side-programming/events/onrowheaderclick)

* [OnViewSelectorClick](https://www.telerik.com/products/aspnet-ajax/documentation/controls/calendar/client-side-programming/events/onviewselectorclick)

* [OnDateClick](https://www.telerik.com/products/aspnet-ajax/documentation/controls/calendar/client-side-programming/events/ondateclick)