/* EF 3.0 要开启 数据库连接复用 MultipleActiveResultSets=true
* 不然会报 The connection does not support MultipleActiveResultSets
* 还会造成后继查询超时(可能因为前一写入操作出异常事务无法提交造成)
* Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
* */