求助，Fatal error: Call to a member function createVo() on a non-object

Fatal error: Call to a member function createVo() on a non-object in E:\webServ\xampp\htdocs\MyAppOnThinkPhp\Lib\Action\IndexAction.class.php on line 9

源码如下：
<?php

class IndexAction extends Action{
   function insert(){
   
      $dao = D("User")；
          $user =  $dao->createVo();
          $user->registerTime = time();
          $user->status = 1;
          $result = $dao->add($user);
          if($result){
             $this->success('用户注册成功');
          }else{
             $this->error('用户注册失败');
          }
   }
/*   function add(){
      $this->display();
   }*/
   
}
?>