Question

I have a method in C# that says FormatSSN that takes a SSN in a string format and replaces the dashes. I mean I am expecting the SSN to be in XXX-XX-XXXX format. I want to write a regular expression that makes sure that the SSN is in the format I have mentioned.

Can anyone help me construct a regular expression??

Answer 1

^\d{3}-\d{2}-\d{4}$

\d is a digit, {X} is repeat the previous element X times.

As Dmitry pointed out in comments, adding ^ at the beginning and $ at the end will cause the regex to only match if the entire string is a SSN. Without those anchors strings like abc123-45-6789xyz would also match.