玛德，数据行都返回过来了，就是没有输出参数！！！
扒官方设计文档：这么一段 雷死人了！！！
When a stored procedure is called using MySqlCommand.ExecuteReader, and the stored procedure has output parameters, the output parameters are only set after the MySqlDataReader returned by ExecuteReader is closed.
原文：http://www.cnblogs.com/micro-chen/p/5666184.html