public class BinaryTreeNode
{
 public BinaryTreeNode Left { get; set; }
 public BinaryTreeNode Right { get; set; }
 public int Data { get; set; }
 public BinaryTreeNode(int data)
 {
  this.Data = data;
 }
}
public void InsertIntoBST(BinaryTreeNode root, int data)
{
  BinaryTreeNode _newNode = new BinaryTreeNode(data);
  BinaryTreeNode _current = root;
  BinaryTreeNode _previous = _current;
  while (_current != null)
  {
   if (data < _current.Data)
   {
    _previous = _current;
    _current = _current.Left;
   }
   else if (data > _current.Data)
   {
    _previous = _current;
    _current = _current.Right;
   }
  }
  if (data < _previous.Data)
   _previous.Left = _newNode;
  else
   _previous.Right = _newNode;
}