I have a RadListBox in a radgrid with the editformtype template and I want to validate that the RadListBox have at least one item. Is there a way to validate that with a FieldValidator.
You can use the built in ASP.NET validation with RadListBox. To validate for selected item of a listbox, just specify the ID of the listbox in the ControlToValidate property of the RequiredFieldValidator. Validation checks to see if there is at least one selected item.