public function sendFile($field = null, $name = null)
    {
        if (!$name && (!$name = $this->getFirstFileName())) {
            return false;
        }
        $file = $this->getFilePath($field, $name);
        if (!$name || !file_exists($file)) {
            throw new NotFoundHttpException;
        }
        \Yii::$app->response->sendFile($file, $name);
    }