C# split string but keep split chars

Question

I'm splitting a string by three different characters but I want the output to include the characters I split by. Is there any easy way to do this?

Answer 1

result = originalString.Split(separator);
for(int i = 0; i < result.Length - 1; i++)
    result[i] += separator;

(EDIT - this is a bad answer - I misread his question and didn't see that he was splitting by multiple characters.)

(EDIT - a correct LINQ version is awkward, since the separator shouldn't get concatenated onto the final string in the split array.)

Answer 2

Recently I wrote an extension method do to this:

public static class StringExtensions
    {
        public static IEnumerable<string> SplitAndKeep(this string s, string seperator)
        {
            string[] obj = s.Split(new string[] { seperator }, StringSplitOptions.None);

            for (int i = 0; i < obj.Length; i++)
            {
                string result = i == obj.Length - 1 ? obj[i] : obj[i] + seperator;
                yield return result;
            }
        }
    }

Answer 3

Regex.Split looks like it might be able to do what you want perhaps.

Answer 4

I'd try:

string[] parts = Regex.Split(originalString, @"(?<=[.,;])")

(if the split chars were , . and ;)

(?<=PATTERN) is positive-lookbehind. It should match at any place where the preceeding text fits PATTERN so there should be a match (and a split) after each occurance of any the characters.

Answer 5

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

namespace ConsoleApplication9
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = @"This;is:a.test";
            char sep0 = ';', sep1 = ':', sep2 = '.';
            string pattern = string.Format("[{0}{1}{2}]|[^{0}{1}{2}]+", sep0, sep1, sep2);
            Regex regex = new Regex(pattern);
            MatchCollection matches = regex.Matches(input);
            List<string> parts=new List<string>();
            foreach (Match match in matches)
            {
                parts.Add(match.ToString());
            }
        }
    }
}

Answer 6

Iterate through the string character by character (which is what regex does anyway. When you find a splitter, then spin off a substring.

pseudo code

int hold, counter;
List<String> afterSplit;
string toSplit

for(hold = 0, counter = 0; counter < toSplit.Length; counter++)
{
   if(toSplit[counter] = /*split charaters*/)
   {
      afterSplit.Add(toSplit.Substring(hold, counter));
      hold = counter;
   }
}

That's sort of C# but not really. Obviously, choose the appropriate function names. Also, I think there might be an off-by-1 error in there.

But that will do what you're asking.

Answer 7

This seems to work, but its not been tested much.

public static string[] SplitAndKeepSeparators(string value, char[] separators, StringSplitOptions splitOptions)
{
    List<string> splitValues = new List<string>();
    int itemStart = 0;
    for (int pos = 0; pos < value.Length; pos++)
    {
        for (int sepIndex = 0; sepIndex < separators.Length; sepIndex++)
        {
            if (separators[sepIndex] == value[pos])
            {
                // add the section of string before the separator 
                // (unless its empty and we are discarding empty sections)
                if (itemStart != pos || splitOptions == StringSplitOptions.None)
                {
                    splitValues.Add(value.Substring(itemStart, pos - itemStart));
                }
                itemStart = pos + 1;

                // add the separator
                splitValues.Add(separators[sepIndex].ToString());
                break;
            }
        }
    }

    // add anything after the final separator 
    // (unless its empty and we are discarding empty sections)
    if (itemStart != value.Length || splitOptions == StringSplitOptions.None)
    {
        splitValues.Add(value.Substring(itemStart, value.Length - itemStart));
    }

    return splitValues.ToArray();
}

Answer 8

Building off from BFree's answer, I had the same goal, but I wanted to split on an array of characters similar to the original Split method, and I also have multiple splits per string (it seems that BFree only has 1 split per string?) Here is the code I came up with:

    public static IEnumerable<string> SplitAndKeep(this string s, char[] delims)
    {
        int start = 0;
        int index = 0;

        while ((index = s.IndexOfAny(delims, start)) != -1)
        {
            index++;
            index = Interlocked.Exchange(ref start, index);

            yield return s.Substring(index, start-index-1);
            yield return s.Substring(start-1, 1);
        }

        if (start < s.Length)
        {
            yield return s.Substring(start);
        }
    }

Answer 9

public static class String_Ext
{
    public static string[] SplitOnGroups(this string str, string pattern)
    {
        var matches = Regex.Matches(str, pattern);
        var partsList = new List<string>();
        for (var i = 0; i < matches.Count; i++)
        {
            var groups = matches[i].Groups;
            for (var j = 0; j < groups.Count; j++)
            {
                var group = groups[j];
                partsList.Add(group.Value);
            }
        }
        return partsList.ToArray();
    }
}

var parts = "abcde  \tfgh\tikj\r\nlmno".SplitOnGroups(@"\s+|\S+");

for (var i = 0; i < parts.Length; i++)
    Print(i + "|" + Translate(parts[i]) + "|");

result:
0|abcde|
1|  \t|
2|fgh|
3|\t|
4|ikj|
5|\r\n|
6|lmno|