Best way to get all digits from a string

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.

score 85 · Accepted Answer · answered Apr 14 '10 at 03:45

85

Do you need to use a Regex?

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

answered Apr 14 '10 at 03:45

Matt Hamilton

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+1, good idea. You left out a bit of the lambda inside the where, though. `.Where(c => Char.IsDigit(c))` – Anthony Pegram Apr 14 '10 at 03:50
Didn't consider approaching this from the char level. – Chris Marisic Apr 14 '10 at 03:58
11

@Anthony No, my syntax works fine, and is less "noisy" than the expanded version. – Matt Hamilton Apr 14 '10 at 03:58
Oh, interesting. I had not tried it that way. – Anthony Pegram Apr 14 '10 at 04:10
4

Upvote for "Do you need to use a Regex" :D – Siewers Oct 14 '13 at 13:41
does this handle floating point and negative numbers? – BenKoshy Nov 23 '17 at 01:10
@BKSpurgeon No, `char.IsDigit('.')` and `char.IsDigit('-')` both return `false`. – Michael Dec 12 '17 at 01:00
Hell yeah my man, Screw regex :) – Jamie Nicholl-Shelley Sep 03 '18 at 12:22

score 23 · Answer 2 · answered Apr 14 '10 at 03:49

23

Have you got something against Replace?

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

answered Apr 14 '10 at 03:49

Alan Moore

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score 10 · Answer 3 · edited Jul 01 '15 at 20:04

10

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",""); //return only numbers from string

edited Jul 01 '15 at 20:04

grant7bar7

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answered Apr 14 '10 at 03:48

maček

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I like this answer. However, between this one and the accepted answer, are there significant difference beside one using Regex and another isn't? – frostshoxx Oct 08 '20 at 23:06

score 6 · Answer 4 · answered Apr 14 '10 at 05:45

6

Just remove all non-digits:

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

answered Apr 14 '10 at 05:45

Konstantin Spirin

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score 0 · Answer 5 · edited Jan 09 '16 at 22:30

0

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)

edited Jan 09 '16 at 22:30

Prix

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answered Apr 14 '10 at 06:27

Jasmeet

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Best way to get all digits from a string

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