getting numbers from a string c#

Question

I have an input string like below:

"/myWS/api/Application/IsCarAvailable/123456/2017"

It is the end of a Web API call that I am making. I need to easily extract the 123456 from the URL.

I was hoping something like the below would work

       string[] numbers = Regex.Split(input, @"\D+");

However, when I set a breakpoint on numbers and run the code it is showing an array of 3 elements?

Element at [0] is ""
Element at [1] is 123456
Element at [2] is 2017

Does anyone see why it would be getting the empty string as the first element?

Not sure about the regular expression, but if the format is guaranteed to be as displayed you might consider `String.Split` and just look at the last two elements. — AlainD, May 31 '17 at 13:47
`string[] numbers = Regex.Replace(input, @"\D+", " ").Trim(' ').Split(' ');` got locked before I could post answer — Slai, May 31 '17 at 14:14

Dmitry Bychenko · Accepted Answer · 2017-05-31T13:51:02.547

5

I suggest matching, not splitting:

   string source = @"/myWS/api/Application/IsCarAvailable/123456/2017";

   string[] numbers = Regex 
     .Matches(source, "[0-9]+") 
     .OfType<Match>()
     .Select(match => match.Value)
     .ToArray();

Please, notice that \d+ in .Net means any unicode digits (e.g. Persian ones: ۰۱۲۳۴۵۶۷۸۹): that's why I put [0-9]+ pattern (RegexOptions.ECMAScript is an alternative if \d+ pattern is preferrable).

edited May 31 '17 at 13:51

answered May 31 '17 at 13:47

Dmitry Bychenko

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can you give a quick comment on the difference in matching and splitting? – Ctrl_Alt_Defeat May 31 '17 at 13:49
1

@Ctrl_Alt_Defeat: matching: is extracting `[0-9]+` (2 items); splitting: using `\D+` delimiter split existing string: `[\D+]123456[\D+]2017` and you have **3** items: *empty*, `123456`, `2017` – Dmitry Bychenko May 31 '17 at 13:54
Thanks for the explanation – Ctrl_Alt_Defeat May 31 '17 at 13:57
Upvoting Dmitry's answer since he was faster than me and more precise in reasoning :-) – K. Berger May 31 '17 at 13:58

score 0 · Answer 2 · answered May 31 '17 at 13:50

0

If your string is always in the same format, this would work:

string numbers = input.Split('/')[input.Split('/').Length - 2];

answered May 31 '17 at 13:50

Icculus018

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score 0 · Answer 3 · answered May 31 '17 at 13:56

I think this is because the split method "splits" the string at the matching expression. So the empty string is the part before the first match. Any reason why you would not use Regex.Matches(input,"\\d+") instead?

        string numtest = "http://www.google.com/test/123456/7890";
        var matchResult = Regex.Matches(numtest, "\\d+");
        for (int i = 0; i < matchResult.Count; i++)
            Console.WriteLine($"Element {i} is {matchResult[i].Value}");

Hope that helps. Regards!

getting numbers from a string c#

3 Answers3