public static BinaryTreeNode BuildBinarySearchTree(int[] sortedArray)  {      if (sortedArray.Length == 0)          return null;         int _mid = sortedArray.Length / 2;      BinaryTreeNode _root = new BinaryTreeNode(sortedArray[_mid]);      int[] _left = GetSubArray(sortedArray, 0, _mid - 1);      int[] _right = GetSubArray(sortedArray, _mid + 1, sortedArray.Length - 1);      _root.Left = BuildBinarySearchTree(_left);      _root.Right = BuildBinarySearchTree(_right);         return _root;  }        public int[] GetSubArray(int[] array, int start, int end)  {      List<int> _result = new List<int>();      for (int i = start; i <= end; i++)      {          _result.Add(array[i]);      }      return _result.ToArray();  }