I am using custom validator with page.isvalid.
This works fine when I create a new page but when I update an existing page I have a bug.

I noticed that when the textbox is empty then page.isvalid works fine (this means that create new pages works).
But the update page doesn't work. When the textbox already has text, pulled from dataRow, then the page.isvalid doesn't work with custom validator.

BUT with the update page, when I clear the textbox and postback to same page, then I enter text into textbox THEN the page.isvalid and custom validator works.

How can I fix this bug????