Registers a control as a trigger for asynchronous postbacks.
Assembly: System.Web.Extensions (in System.Web.Extensions.dll)
The method enables you to register Web server controls as triggers so that they perform an asynchronous postback instead of a synchronous postback. When the ChildrenAsTriggers property of an UpdatePanel control is set to true (which is the default), postback controls inside the UpdatePanel control are automatically registered as asynchronous postback controls.
Use the method to register controls outside an UpdatePanel control as triggers for asynchronous postbacks, and to potentially update the content of an update panel. To update an UpdatePanel control programmatically, call the Update method.
You can add the trigger declaratively by using the Triggers element of the UpdatePanel control. In Visual Studio, use the designer's UpdatePanelTrigger Collection Editor dialog box.
The following example shows how to call the method to register a Button control so that it causes an update of an UpdatePanel control's content. The Button control is not inside the UpdatePanel control. Two buttons are shown: Button1 and Button2. Button1 refreshes the content of the panel, and Button2 refreshes the whole page.
The following example shows how to call the method to register a user control so that it causes an update of an UpdatePanel control's content. The first example shows a page using the user control. The second example shows the user control.