Regex to match all us phone number formats

Question

First of all i would say i have seen many example here and googled but none found that matches all the condition i am looking for some match top 3 not below some inbetween.

Answer 1

for c#, the for US phone number validation should be like below

^\(?\d{3}?\)??-??\(?\d{3}?\)??-??\(?\d{4}?\)??-?$

777-777-7777