the screen has a tabControl, so many controls are hidden/now-showing until you open that tabItem. when performing validation, some of these non-visible controls are invalid, but the ValidationSummary is not showing them, not until i open a tabItem that contains those controls with invalid data.
how to make the validationSummary show all errors?
I found similar thread, but the proposed answer doesn't work at all. Validation Summary in TabControl (Silverlight 4)