What is correct sytnax for setting an AsyncPostBackTrigger for an UpdatePanel with an asp:ButtonField from an GridView control?

I need to set an 'AsyncPostBackTrigger' for each asp:ButtonField in my GridView

Here is my source code

Update

I need to keep the UpdateMode and ChildrenAsTriggers attributes set to true because the I have other button contained within the UpdatePanel that do not refresh the UpdatePanel control