# RequestStart event

The `RequestStart` client-side event handler is called when a request to the server is started.

The event can be initially triggered by an initiating control configured in the AjaxManager settings, a control within an AjaxPanel, or by a client-side `ajaxRequest()` call. The event can be cancelled.

Two parameters are passed to the event handler with the following methods:

* `sender`—The instance of the client-side `RadAjaxManager` or `RadAjaxPanel` object.

* `eventArgs`—Provides the following methods:

  * `set_cancel()`—Lets you permit or block the AJAX request from continuing. Calling `set_cancel(true)` prevents the request from continuing.

  * `get_eventTarget()`—Gets the `UniqueID` of the element that had raised the request.

  * `get_eventArgument()`—Gets the string passed in the initial AJAX request.

  * `get_eventTargetElement()`—Gets the instance of the client-side object that raised the AJAX request. You can iterate each of the settings and retrieve the initiating control `id` and another array of objects that represent updated controls.

  * `get_ajaxSettings()`—Returns an array of objects that represents AjaxManager current configuration of the AjaxManager or the updated controls of the AjaxPanel.

  * `get_enableAjax()`, `set_enableAjax()`—Gets or sets if an AJAX request is performed. `set_enableAjax(false)` causes the request to be performed with a standard postback.

The example below displays the control that initiated the request.

```ASP.NET
<script type="text/javascript">
	function requestStart(sender, eventArgs) {
	    alert('Request start initiated by: ' + eventArgs.get_eventTarget());
	}
</script>
<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
	<ClientEvents OnRequestStart="requestStart" />
</telerik:RadAjaxManager>
```

## See Also

* [AjaxManager Overview](https://www.telerik.com/products/aspnet-ajax/documentation/controls/ajaxmanager/overview)
* [Demo: AjaxManager Client-Side API](https://demos.telerik.com/aspnet-ajax/ajax/examples/manager/clientsideapi/defaultcs.aspx)