Can't match string using regular expression with "?"

Question

I need to build regular expression to match following strings:

1. CCN
2. CreditCardNum
3. CreditCardNUmber
4. CCNumber

etc.

I built it as follows : C(redit)?C(ard)?N(um|umber)?
It doesn't match "CreditCardNumber" string.
I also tried : C(redit)?C(ard)?N(:?um|umber) without success

Answer 1

Your pattern is good, all you need to add is: (?i) at the begining

or IgnoreCase in the regex options. RegexOptions.IgnoreCase

Note: since you don't need to capture "redit" or "ard", non capturing groups (?:...) are better:

(?i)C(?:redit)?C(?:ard)?N(?:um(?:ber)?)?

If you want to have more control with the case:

C(?i:redit)?C(?i:ard)?N(?i:um(?:ber)?)?

For more security you can add word boundaries at the begining and at the end of the pattern \b