如何动态创建UpdatePanel触发器

I have an UpdatePanel in my default.aspx page and the UpdatePanel has asp placeholder, also I have an ascx control that is the navigation of the site and it is created dynamically based on the data in the database, each navigation item is an ImageButton, and my each loop in DataList has HiddenField value of the URL for each corresponded ascx control like Value="~/controls/somecontrol.ascx"I have an UpdatePanel in my default.aspx page a