Best way to get all digits from a string with regex

Question

Is there any better way to get take a string such as "(123) 455-2344" and get "1234552344" from it than doing this:

var matches = Regex.Matches(input, @"[0-9]+", RegexOptions.Compiled);

return String.Join(string.Empty, matches.Cast<Match>()
                                .Select(x => x.Value).ToArray());

Perhaps a regex pattern that can do it in a single match? I couldn't seem to create one to achieve that though.

Answer 1

Do you need to use a Regex?

return new String(input.Where(Char.IsDigit).ToArray());

Answer 2

You'll want to replace /\D/ (non-digit) with '' (empty string)

Regex r = new Regex(@"\D");
string s = Regex.Replace("(123) 455-2344", r, "");

Or more succinctly:

string s = Regex.replace("(123) 455-2344", @"\D");

Answer 3

Have you got something against Replace?

return Regex.Replace(input, @"[^0-9]+", "");

Answer 4

Just remove all non-digits:

var result = Regex.Replace(input, @"\D", "");

Answer 5

In perl (you can adapt this to C#) simply do $str =~ s/[^0-9]//g;

I am assuming that your string is in $str. Basic idea is to replace all non digits with '' (i.e. empty string)