How can I make a File Attachment control conditionally required?

Question

How can I make a File Attachment control conditionally required? For other controls, such as a text box I can add a data validation rule that and's the condition (a checkbox being checked) and the control's isBlank. However, File Attachment controls lack this function (data validation), so how can I emulate it?

Answer 1

Did you try checking the box Cannot be blank in the properties window?

Right click on the control, properties, Cannot be blank.