AjaxControlToolkit.UpdatePanelAnimationExtender.OnPreRender C# (CSharp) Method

        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);

            ResolveControlIDs(_updating);
            ResolveControlIDs(_updated);
            ReplaceStaticAnimationTargets(_updating);
            ReplaceStaticAnimationTargets(_updated);

            var targetPanel = TargetControl as UpdatePanel;
            foreach(var trigger in targetPanel.Triggers) {
                var asyncTrigger = trigger as AsyncPostBackTrigger;

                if (asyncTrigger == null)
                    continue;

                var triggerControlClientID = FindControl(asyncTrigger.ControlID).ClientID;
                _triggerControlsClientID.Add(triggerControlClientID);
            }
        }