I've been looking on the interwebs for some set of instructions that can show me how I can create a popup error message when one attempts to insert a null value on a gridview when it's set to not allow nulls in the database. I'm pretty sure I've been looking up the wrong terminology as I haven't seen anything that resembles what I'm looking for.
Basically what I need is an error popup/window to appear, when a field on a gridview is supposed to have a value entered and is left blank, stating 'You're supposed to fill in blah blah blah...'
I tried using NullDisplayText but that doesn't seem to work for what I need. I've searched for various searches for gridview null popup. I've even searched on Javascript solutions but with no luck.
Am I just searching for the wrong terms or has no one even attempted this at all?