Regular expressions C# - is it possible to extract matches while matching?

Question

Say, I have a string that I need to verify the correct format of; e.g. RR1234566-001 (2 letters, 7 digits, dash, 1 or more digits). I use something like:

        Regex regex = new Regex(patternString);
        if (regex.IsMatch(stringToMatch))
        {
            return true;
        }
        else
        {
            return false;
        }

This works to tell me whether the stringToMatch follows the pattern defined by patternString. What I need though (and I end up extracting these later) are: 123456 and 001 -- i.e. portions of the stringToMatch.

Please note that this is NOT a question about how to construct regular expressions. What I am asking is: "Is there a way to match and extract values simultaneously without having to use a split function later?"

Answer 1

You can use regex groups to accomplish that. For example, this regex:

(\d\d\d)-(\d\d\d\d\d\d\d)

Let's match a telephone number with this regex:

var regex = new Regex(@"(\d\d\d)-(\d\d\d\d\d\d\d)");
var match = regex.Match("123-4567890");
if (match.Success)
    ....

If it matches, you will find the first three digits in:

match.Groups[1].Value

And the second 7 digits in:

match.Groups[2].Value

P.S. In C#, you can use a @"" style string to avoid escaping backslashes. For example, @"\hi\" equals "\\hi\\". Useful for regular expressions and paths.

P.S.2. The first group is stored in Group[1], not Group[0] as you would expect. That's because Group[0] contains the entire matched string.