C# split string but keep separators

Question

There already exist similar questions, but all of them use regexen. The code I'm using (that strips the separators):

string[] sentences = s.Split(new string[] { ". ", "? ", "! ", "... " }, StringSplitOptions.None);

I would like to split a block of text on sentence breaks and keep the sentence terminators. I'd like to avoid using regexen for performance. Is it possible?

Possible duplicate http://stackoverflow.com/questions/521146/c-split-string-but-keep-split-chars — Matthew Abbott, Apr 11 '11 at 17:53
Funny. The title of the duplicate is "C# split string but keep split chars". — , Apr 11 '11 at 17:56
@rerun: This will be ran on a very large file and regex splitting takes up to three times as long as the `String` methods. — Isaac G., Apr 11 '11 at 18:00

JaredPar · Answer 1 · 2011-04-11T17:59:59.653

6

I don't believe there is an existing function that does this. However you can use the following extension method.

public static IEnumerable<string> SplitAndKeepSeparators(this string source, string[] separators) {
  var builder = new Text.StringBuilder();
  foreach (var cur in source) {
    builder.Append(cur);
    if (separators.Contains(cur)) {
      yield return builder.ToString();
      builder.Length = 0;
    }
  }
  if (builder.Length > 0) {
    yield return builder.ToString();
  }
}

edited Apr 11 '11 at 17:59

answered Apr 11 '11 at 17:52

JaredPar

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It seems like this will break for the last field? – Apr 11 '11 at 17:58
@jfs, @pst whoops, forgot to add in the final check – JaredPar Apr 11 '11 at 18:00
1

`if (separators.Contains(cur))` won't compile. – Isaac G. Apr 11 '11 at 18:20
@Isaac G. `using System.Linq;` (This is because `Contains` is an Extension Method from LINQ) – Apr 14 '11 at 01:29
1

This is completely broken. “cur” is a `char`, “separators” is a `string[]`. “`separators.Contains(cur)`” makes no sense. – Timwi May 14 '13 at 10:35

C# split string but keep separators

1 Answers1