regex check for closed parenthesis code example

Example: c# balanced regex all text in brackets

Regex re = new Regex(string.Format(@"^
  {0}                       # Match first opeing delimiter
  (?<inner>
    (?>
        {0} (?<LEVEL>)      # On opening delimiter push level
      | 
        {1} (?<-LEVEL>)     # On closing delimiter pop level
      |
        (?! {0} | {1} ) .   # Match any char unless the opening   
    )+                      # or closing delimiters are in the lookahead string
    (?(LEVEL)(?!))          # If level exists then fail
  )
  {1}                       # Match last closing delimiter
  $", "<quote>", "</quote>"), 
  RegexOptions.IgnorePatternWhitespace | RegexOptions.IgnoreCase);
re.Match("<quote>inner text</quote>").Groups["inner"].Value == "inner text"
re.Match("<quote>a<quote>b</quote>c</quote>").Groups["inner"].Value == "a<quote>b</quote>c"