Question

I’m currently trying to match and capture text in the following input:

field: one two three field: "moo cow" field: +this

I can match the field: with [a-z]*\: however I can’t seem to match the rest of the content so far my attempts have only resulted in capturing everything which is not what I want to do.

Answer 1

If you know that it is always going to be literally field: there is absolutely no need for a regular expression:

var delimiters = new String[] {"field:"};
string[] values = input.Split(delimiters, StringSplitOptions.RemoveEmptyEntries);

---

However, from your regex I assume that the name field can vary, as long as it’s in front of a colon. You could try to capture a word followed by : and then everything up to the next of those words (using a lookahead).

foreach(Match match in Regex.Matches(input, @"([a-z]+):((?:(?![a-z]+:).)*)"))
{
    string fieldName = match.Groups[1].Value;
    string value = match.Groups[2].Value;
}

An explanation of the regular expression:

(     # opens a capturing group; the content can later be accessed with Groups[1]
[a-z] # lower-case letter
+     # one or more of them
)     # end of capturing group
:     # a literal colon
(     # opens a capturing group; the content can later be accessed with Groups[2]
(?:   # opens a non-capturing group; just a necessary subpattern which we do not
      # need later any more
(?!   # negative lookahead; this will NOT match if the pattern inside matches
[a-z]+:
      # a word followed by a colon; just the same as we used at the beginning of
      # the regex
)     # end of negative lookahead (not that this does not consume any characters;
      # it LOOKS ahead)
.     # any character (except for line breaks)
)     # end of non-capturing group
*     # 0 or more of those
)     # end of capturing group

So first we match anylowercaseword:. And then we match one more character at a time, for each one checking that this character is not the start of anotherlowercaseword:. With the capturing groups we can then later separately find the field’s name and the field’s value.