How can call the depth of decision tree like the array using brackets [i]

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C#

trees

Hello everyone,
I am designing a chess engine for my project instead of playing random: http://www.youtube.com/watch?v=8EKKTMPFY8g[^]

i am planning to use greedy MinMax algorithm, so i first started with writing the data structure

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace AI
{
    class Node
    {
        #region Constructor

        public Node(object data)
        {
            this.Data = data;
        }

        #endregion

        #region Properties

        private int _order;
        private object _data;
        private Node _parent;
        private List<Node> _childern = new List<Node>();

        public object Data
        {
            get { return _data; }
            set { _data = value; }
        }

        public Node Parent
        {
            get { return _parent; }
            set { _parent = value; }
        }

        public List<Node> Children
        {
            get { return _childern; }
            set { _childern = value; }
        }

        public int Order
        {
            get { return _order; }
            set { _order = value; }
        }

        #endregion

        #region Methods

        public void AddChild(Node next_node)
        {
            next_node._order = this.Order + 1;
            next_node.Parent = this;
            this.Children.Add(next_node);
        }

        public void AddChild(object next_node_data)
        {
            Node next_node = new Node(next_node_data);
            AddChild(next_node);
        }

        #endregion
    }

    class Tree
    {
        #region Constructor

        public Tree(object root_data)
        {
            this.Root = new Node(root_data);
            this.Root.Order = 0;
            this.length = 1;
        }

        public Tree(Node root_node)
        {
            Root = root_node;
        }

        #endregion

        #region Properties

        private Node _root;
        private int _length;

        public Node Root
        {
            get { return _root; }
            set { _root = value; }
        }

        public int length
        {
            get { return _length; }
            set { _length = value; }
        }

        #endregion
    }
}

I have a problem, once i have a evaluated the tree, and want to compare to see which is the best move, how can return to 1st order node without using a recursive method for example like array use [i] but i is no the length i is the depth if the tree

Thanks in advance,
z3ngew