I have a uniqueness constraint on my SQL Server table. I want to check for uniqueness in a rule before getting an error in SQL Server. I added a rule in the rule class. However, the SQL error is triggering before the rule code is ever run.

I tried to put this code in the HookPreSave method but it wouldn't let me call the mmAppDeskTop.FormMgr.Show() method, so I'm not sure how to tell the user what the problem is. Would I just add a broken rule from here?

Then I tried the Validating method of the text box but I don't see a way to indicate that the value is not valid. For now, I have just forced the value to blank so it will get trapped by the test for blank id's but that's not a great solution.

What's the best way to handle this? Thanks.