System.Text.RegularExpressions.Regex.GetGroupNumbers C# (CSharp) Method

        public int[] GetGroupNumbers()
        {
            throw null;
        }

        protected Rule(string parsePattern)
        {
            RulePattern = new Regex(parsePattern, RegexOptions.Singleline);

            var regexGroupsAmount = RulePattern.GetGroupNumbers().Length;
            if (regexGroupsAmount != 4)
                throw new Exception(string.Format(IncorrectPatternMsg, this.GetType().FullName));
        }