Split string by array of strings, and include words used to split in final array in C#

Question

I'm trying to split a string into an array around words in a string array. Right now, I'm using myString.Split(arrayOfWordsToSplitOn, StringSplitOptions.RemoveEmptyEntries), which splits the string, but doesn't include the actual word that it is splitting on.

For example, if I have the string "My cat and my dog are very lazy", and a string array {"cat", "dog"}, right now it returns {"My", "and my", "are very lazy"}.

However, I would like to have the final output be {"My", "cat", "and my", "dog", "are very lazy"}. Is there any way to do this?

Do you want to split on word boundaries or also substrings? Your current String.Split approach does the latter — Tim Schmelter
– Tim Schmelter, Commented Mar 10, 2017 at 15:11
Still a regex would be good to use: Regex.Split(s, string.Format(@"\b({0})\b", string.Join("|", arrayOfWordsToSplitOn))) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Mar 10, 2017 at 15:12
Sorry, I understand that word is ambiguous. I'm trying to build a dictionary definition that contains links for words that match other dictionary definitions. I already do a query to determine the list of words that will be linking to other terms. This array will be what I need to split on, so that the linked terms are separate entities in the array. — OstrichGlue
– OstrichGlue, Commented Mar 10, 2017 at 15:13

Wiktor Stribiżew · Accepted Answer · 2017-03-10 15:16:38Z

4

You may create an alternation based regex out of your list of search words, and wrap that part with a capturing group, (...). Then, add \s* to strip the whitespaces around the group and use Regex.Split:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
    public static void Main()
    {
        var arrayOfWordsToSplitOn = new List<string> { "cat", "dog" };
        var s = "My cat and my dog are very lazy";
        var pattern = string.Format(@"\s*\b({0})\b\s*", string.Join("|", arrayOfWordsToSplitOn));
        var results = Regex.Split(s, pattern).Where(x => !String.IsNullOrWhiteSpace(x)).ToList();
        foreach (var res in results)
            Console.WriteLine(res);
    }
}

See the C# demo.

Results:

My
cat
and my
dog
are very lazy

NOTES:

If the search words can contain non-word chars, the pattern should be adjusted as \b (word boundaries) might fail the match, and the search "words" will have to be Regex.Escaped
The search word array might need sorting by length and alphabet if you decide to drop word boundaries.

answered Mar 10, 2017 at 15:16

Wiktor Stribiżew

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1 Comment

Callum Linington Over a year ago

awesome answer, makes it so easy

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