I am using the maskinput like this:

"PhoneNumber"].MaskInput = "(###) ###-#### Ext. #####";

My problem is user may input only part of the phone number , such as without area code or input extension only. and the extension may only have 3 or 4 digit. in these case, the mask think the input is not valide.

My question is how can I show this mask but also have the ability to allow user input just part of the phone numbers?

Thanks