How do I make a checkbox required on an ASP.NET form?

I’ve done some searching on this, and I’ve found several partial answers, however nothing that gives me that warm fuzzy “this is the right way to do this”. To answer the most frequently occurring complaint against this question: “checkboxes can have two legitimate states – checked and unchecked”, this is an “I accept the terms and conditions…” checkbox which must be checked in order to complete a registration, hence checking the box is required from a business logic standpoint.

OnCheckedChanged event not firing

I have a GridView with a column of checkboxes (the rest of the GridView is being populated from a database). I’m using AJAX to perform different functions, and I’m wondering if i’m just not calling the OnCheckedChanged event in the right place. Should it be wrapped in some sort of UpdatePanel? I’m still really new to how all of this works…basically what I’m aiming for is to change a bit value in my database when a checkbox is checked. I know the logic of how to do that, I just don’t know if I’m addressing my OnCheckedChanged event the right way.