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();
}