title: Inheriting From Sealed Classes
body: <p>Lets say I have a Phone number my classes need to validate and keep track of and for the most part a phone number is just a string so in an attempt to be DRY one would just create a Phone class and inherit from string.  Since I can't do that what is the next best approach?  Adding a string as a private member and overloading the equal/= operators so it can be passed and set as a string?</p>