Is there a way, using a mask setting of (000) 000-0000 for a phone number, that would also allow no phone # to be entered? That is, either require the full phone # to be entered or none at all. I found this ticket from many years ago: ASPxGridView (Editors) - provide the ability to use null values in editors where a mask is specified, is that still accurate, or is there hopefully a simpler way to do this without going down the rabbit hole of regular expressions?
Please refer to the ASPxTextBox - How to allow null value when a regular expression and a mask are applied thread. It describes how to accomplish a similar task.
While this solution uses ReqularExpression, it is not a requirement: the main idea is to specify an optional numeric mask with the "9" character: Mask Types.