How to add Trigger to an UpdatePanel in code behind

//Creates a new async trigger
AsyncPostBackTrigger trigger = new AsyncPostBackTrigger();
            //Sets the control that will trigger a post-back on the UpdatePanel
trigger.ControlID = "btnCommit";
//Sets the event name of the control
trigger.EventName = "Click";
//Adds the trigger to the UpdatePanels' triggers collection
pnlMain.Triggers.Add(trigger);