Best way to get all digits from a string [duplicate]

Question

Is there any better way to get take a string such as "[phone]" 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.

Discus

Answer 1

Do you need to use a Regex?

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

Doriadorian

+1, good idea. You left out a bit of the lambda inside the where, though. .Where(c => Char.IsDigit(c)) – Jaclin

Didn't consider approaching this from the char level. – Discus

@Anthony No, my syntax works fine, and is less "noisy" than the expanded version. – Doriadorian

Oh, interesting. I had not tried it that way. – Jaclin

Upvote for "Do you need to use a Regex" :D – Bedroll

does this handle floating point and negative numbers? – Overhang

@BKSpurgeon No, char.IsDigit('.') and char.IsDigit('-') both return false. – Chester

Hell yeah my man, Screw regex :) – Colonel

Answer 2

Have you got something against Replace?

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

Lignite

Answer 3

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

Regex r = new Regex(@"\D");
string s = Regex.Replace("[phone]", r, "");

Or more succinctly:

string s = Regex.Replace("[phone]", @"\D",""); //return only numbers from string

Hose

I like this answer. However, between this one and the accepted answer, are there significant difference beside one using Regex and another isn't? – Fowle

Answer 4

Just remove all non-digits:

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

Lark

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)

Bethesde