Regex replace by group in C#

Question

I am trying to using regex replace in C# although I am having some issues getting the pattern to align correctly. What I am looking to do is replace certain combinations as per the first 2 groups but not if it matches the pattern of the 3rd group. What I have so far is

 var pattern = @"(,)|(\[\{)|(^:\[[*]])";

 string NewLineValue = Regex.Replace(LineValue, pattern,Environment.NewLine);

Essentially I want to replace all comma's or [{ combinations in a string but not if the comma appears within [[]] characters (e.g [[1234,5678]])

Any help is much appreciated...

The character "^" when placed inside square brackets is used to make a negated character class. The way you used it, in the third group, will only mean that it's the beginning of the text. — shwartz
– shwartz, Commented Dec 24, 2018 at 15:18
An short input example and desired output could help. Also, in case you're not trying to parse a JSON file like @CamiloTerevinto guessed (you could have it easier, if you are), try using a negative lookahead. See: regular-expressions.info/lookaround.html — shwartz
– shwartz, Commented Dec 24, 2018 at 15:33
@CamiloTerevinto that is the end goal, however at the moment I am trying to put some of the entries into a readable format for the end user to determine what elements are required.... the line items in the file do not follow a consistent format either as they are activity log entries and change line by line. — J B
– J B, Commented Dec 24, 2018 at 17:13
@shwartz, thank you. would you be able to elaborate as to where the "^" symbol would need to be placed in order to ignore the "," if it appears within a [[x]] section? your advice is much appreciated. — J B
– J B, Commented Dec 24, 2018 at 17:15

Wiktor Stribiżew · Accepted Answer · 2018-12-24 17:49:19Z

4

You need to match and capture all substrings between [[ and ]] (to be restored in the resulting string) and then match , or [{ in all other contexts to replace with a newline:

var pattern = @"(?s)(\[\[.*?]])|,|\[{";
var result = Regex.Replace(s, pattern, m => 
    m.Groups[1].Success ? m.Groups[1].Value : Environment.NewLine);

The pattern matches:

(?s) - a RegexOptions.Singleline inline option
(\[\[.*?]]) - Group 1: [[, any 0+ chars, as few as possible, and then ]]
| - or
, - a comma
| - or
\[{ - [{ substring.

If Group 1 matches (m.Groups[1].Success), the match is pasted back (m.Groups[1].Value), else, the match (, or [{) is replaced with a Environment.NewLine.

answered Dec 24, 2018 at 17:49

Wiktor Stribiżew

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