Count the number of times a string appears within a string

Question

I simply have a string that looks something like this:

"7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false"

All I want to do is to count how many times the string "true" appears in that string. I'm feeling like the answer is something like String.CountAllTheTimesThisStringAppearsInThatString() but for some reason I just can't figure it out. Help?

http://stackoverflow.com/questions/541954/how-would-you-count-occurences-of-a-string-within-a-string-c/542136#542136 — jball, Jun 10 '10 at 16:59
@jball I think all the solutions there are for counting occurrences of a *character* — AakashM, Jun 10 '10 at 17:56
@AakashM, look at the second link. Also, this is the perfect opportunity to provide a more correct (i.e., string based, not char based) answer to that question. — jball, Jun 10 '10 at 18:46
I'm glad you don't work for Microsoft and get to name methods! — user3791372, Sep 28 '16 at 10:18
The linked questions ("This question already has answers here: ") has mostly answers for counting multiple character occurrences, not multiple substring occurrences. — Alex P., Jun 07 '23 at 13:56

score 208 · Accepted Answer · edited Dec 04 '17 at 18:59

208

Regex.Matches(input, "true").Count

edited Dec 04 '17 at 18:59

Chris Benard

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answered Jun 10 '10 at 16:53

µBio

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2

Based on brevity alone - you win ;) – Paul Mignard Jun 10 '10 at 18:36
1

there is no matches in C# string. oops. Regex. Nevermind – xarzu Feb 05 '14 at 14:31
1

Why are we escaping `input` it's not a regular expression? – tpower Aug 02 '17 at 09:00
@tpower, same question I had. I researched `Regex.Escape` and ran tests in LINQPad to confirm. I edited the edit to remove that. – Chris Benard Dec 04 '17 at 19:00

score 17 · Answer 2 · answered Jun 10 '10 at 17:27

Probably not the most efficient, but think it's a neat way to do it.

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(CountAllTheTimesThisStringAppearsInThatString("7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false", "true"));
        Console.WriteLine(CountAllTheTimesThisStringAppearsInThatString("7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false", "false"));

    }

    static Int32 CountAllTheTimesThisStringAppearsInThatString(string orig, string find)
    {
        var s2 = orig.Replace(find,"");
        return (orig.Length - s2.Length) / find.Length;
    }
}

ha ha - I should mark yours as correct just for using my proposed method name. :) — Paul Mignard, Jun 11 '10 at 18:58

score 14 · Answer 3 · edited Apr 24 '16 at 10:15

14

Your regular expression should be \btrue\b to get around the 'miscontrue' issue Casper brings up. The full solution would look like this:

string searchText = "7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false";
string regexPattern = @"\btrue\b";
int numberOfTrues = Regex.Matches(searchText, regexPattern).Count;

Make sure the System.Text.RegularExpressions namespace is included at the top of the file.

edited Apr 24 '16 at 10:15

StuartLC

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answered Jun 10 '10 at 17:22

DonaldRay

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The string variable should not be called Regex - it collides with the .NET Regex class name itself. – JustAMartin Apr 08 '15 at 16:42

score 5 · Answer 4 · edited Aug 05 '13 at 13:50

5

This will fail though if the string can contain strings like "miscontrue".

   Regex.Matches("7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false", "true").Count;

edited Aug 05 '13 at 13:50

Sangram Nandkhile

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answered Jun 10 '10 at 16:58

Sploofy

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score 4 · Answer 5 · answered Jun 10 '10 at 17:46

4

Here, I'll over-architect the answer using LINQ. Just shows that there's more than 'n' ways to cook an egg:

public int countTrue(string data)
{
    string[] splitdata = data.Split(',');

    var results = from p in splitdata
            where p.Contains("true")
            select p;

    return results.Count();
}

answered Jun 10 '10 at 17:46

Robaticus

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Thanks its work fine and smart too :) – Syed Mohamed Aug 14 '14 at 09:15

score 3 · Answer 6 · answered Jun 10 '10 at 17:08

3

With Linq...

string s = "7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false";
var count = s.Split(new[] {',', ':'}).Count(s => s == "true" );

answered Jun 10 '10 at 17:08

Jace Rhea

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score 2 · Answer 7 · answered Jun 10 '10 at 17:00

2

do this , please note that you will have to define the regex for 'test'!!!

string s = "7,true,NA,false:67,false,NA,false:5,false,NA,false:5,false,NA,false";
string[] parts = (new Regex("")).Split(s);
//just do a count on parts

answered Jun 10 '10 at 17:00

VoodooChild

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Count the number of times a string appears within a string

7 Answers7

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