How to validate a specific format phone number?

Question

My numbers looks like (###) ###-####

There is a space between the ) and the next digit or my number can look like (###) ###-#### ext ####

space after the ext and the )

Can someone tell me what regex needs to be performed to verify if either one is valid. Please note that the extension needs to be 4 digits if one is present.

I found this RegEx expression on the web

Regex.Match(number, @"^(\+[0-9]{9})$").Success

Unfortunately I am not very good at RegEx to understand or modify that

Answer 1

这个模式怎么样：

@"^\(\d{3}\) \d{3}-\d{4}( ext \d{4}){0,1}$"