Regex replace commas within parentheses C#

Question

I\'m having a hell of a time replacing commas only within parentheses for this string:

select distinct \\n(\'\'+rtrim(ent.custno)+\' - \'+rtrim(ent.com

Answer 1

Assuming your parentheses are paired and can be nested (balanced), and you need to replace all commas inside those balanced parentheses, you can use a regex to match those substrings and replace the commas with a match evaluator:

cols = Regex.Replace(cols, @"\((?>[^()]|(?)\(|(?<-c>)\))*(?(c)(?!))\)", m => m.Value.Replace(",", ";"));

See IDEONE demo