public function actionNavdel($id)
 {
     $model = AgNav::findOne($id);
     if ($model->delete()) {
         AgNavbar::deleteAll("nid={$id}");
         AgNavitem::deleteAll("nid={$id}");
         Yii::$app->getSession()->setFlash('info', '删除成功!');
         return $this->redirect(['index']);
     }
 }