System.Text.RegularExpressions.RegexReplacement.RegexReplacement C# (CSharp) Method

        internal RegexReplacement(string rep, RegexNode concat, Hashtable _caps)
        {
            if (concat.Type() != RegexNode.Concatenate)
                throw new ArgumentException(SR.ReplacementError);

            StringBuilder sb = StringBuilderCache.Acquire();
            List<string> strings = new List<string>();
            List<int> rules = new List<int>();

            for (int i = 0; i < concat.ChildCount(); i++)
            {
                RegexNode child = concat.Child(i);

                switch (child.Type())
                {
                    case RegexNode.Multi:
                        sb.Append(child._str);
                        break;

                    case RegexNode.One:
                        sb.Append(child._ch);
                        break;

                    case RegexNode.Ref:
                        if (sb.Length > 0)
                        {
                            rules.Add(strings.Count);
                            strings.Add(sb.ToString());
                            sb.Length = 0;
                        }
                        int slot = child._m;

                        if (_caps != null && slot >= 0)
                            slot = (int)_caps[slot];

                        rules.Add(-Specials - 1 - slot);
                        break;

                    default:
                        throw new ArgumentException(SR.ReplacementError);
                }
            }

            if (sb.Length > 0)
            {
                rules.Add(strings.Count);
                strings.Add(sb.ToString());
            }

            StringBuilderCache.Release(sb);

            _rep = rep;
            _strings = strings;
            _rules = rules;
        }