System.Text.RegularExpressions.Match.LastGroupToStringImpl C# (CSharp) Method

        internal string LastGroupToStringImpl()
        {
            return GroupToStringImpl(_matchcount.Length - 1);
        }

 /// <summary>
 /// Given a Match, emits into the List<String> the evaluated
 /// Right-to-Left substitution pattern.
 /// </summary>
 private void ReplacementImplRTL(List<String> al, Match match)
 {
     for (int i = _rules.Count - 1; i >= 0; i--)
     {
         int r = _rules[i];
         if (r >= 0)  // string lookup
             al.Add(_strings[r]);
         else if (r < -Specials) // group lookup
             al.Add(match.GroupToStringImpl(-Specials - 1 - r));
         else
         {
             switch (-Specials - 1 - r)
             { // special insertion patterns
                 case LeftPortion:
                     al.Add(match.GetLeftSubstring());
                     break;
                 case RightPortion:
                     al.Add(match.GetRightSubstring());
                     break;
                 case LastGroup:
                     al.Add(match.LastGroupToStringImpl());
                     break;
                 case WholeString:
                     al.Add(match.GetOriginalString());
                     break;
             }
         }
     }
 }