What is the difference between AsyncPostBackTrigger & PostBackTrigger?

Question

What is the difference between AsyncPostBackTrigger & PostBackTrigger?

Answer 1

Controls inside an UpdatePanel by default cause a partial page update, controls outside cause a postback, using these triggers it is possible to change this behaviour as required.

From http://seminaarit.codezone.fi/video/devdays-2007/track1/2/2-ASP-dotNET_AJAX_Extensions.ppt: (dead link)

AsyncPostBackTrigger

• Converts postbacks into async callbacks * Typically used to trigger updates when controls outside an UpdatePanel post back * If ChildrenAsTriggers="false", can be used to specify which controls inside UpdatePanel should call back rather than post back

PostBackTrigger

• Lets controls inside UpdatePanel post back. * Typically used to allow certain controls to post back when ChildrenAsTriggers="true"

Answer 2

Here's a blog post which explains the difference:

In the template in an update panel, there are the options of an AsyncPostBackTrigger or a PostBackTrigger.

By default, controls outside of an update panel will trigger a normal synchronous post back. The AsyncPostBackTrigger “wires” up these controls to trigger an asynchronous post back. Conversely, controls declared inside an update panel will trigger an asynchronous call by default. The PostBackTrigger short circuits this, and forces the control to do a synchronous post back.