RadixTree.Tree.FindSuccessorRec C# (CSharp) Method

        private string FindSuccessorRec(string wordPart, Node curNode,string carry)
        {
            var matches = MatchingConsecutiveCharacters(wordPart, curNode);

            if ((matches == 0) || (curNode == _root) ||
                ((matches > 0) && (matches < wordPart.Length) ))
            {

                var newLabel = wordPart.Substring(matches, wordPart.Length - matches);
                foreach (var child in curNode.SubNodes)
                    if (child.Label.StartsWith(newLabel[0].ToString()))
                        return FindSuccessorRec(newLabel, child, carry + curNode.Label);

                return curNode.Label;
            }
            else if (matches < curNode.Label.Length)
            {
                return carry + curNode.Label;
            }
            else if (matches == curNode.Label.Length)
            {
                carry = carry + curNode.Label;

                int min = int.MaxValue;
                int index = -1;
                for (int i = 0; i < curNode.SubNodes.Count;i++ )
                    if (curNode.SubNodes[i].Label.Length < min)
                    {
                        min = curNode.SubNodes[i].Label.Length;
                        index = i;
                    }

                if (index > -1)
                    return carry + curNode.SubNodes[index].Label;
                else
                    return carry;
            }
            else return string.Empty;
        }