public int Height()
        {
            if(this.Root == null)
            {
                return -1;
            }
           return Height(this.Root);
        }
        private int Height (BinaryTreeNode node)
        {
            if (this.Root.LeftChild == null && this.Root.RightChild == null)
            {
                return 0;
            }

            int leftHeight = 0;
            int rightHeight = 0;

            if (this.Root.LeftChild != null)
            {
                leftHeight = Height(this.Root.LeftChild);
            }
            if (this.Root.RightChild != null)
            {
                rightHeight = Height(this.Root.RightChild);
            }
            return Math.Max(++leftHeight, ++rightHeight);
        }