An error occurred while starting a transaction on the provider connection. See the inner exception for details.

用EntityFramework循环操作数据时，报了如下错误 

An error occurred while starting a transaction on the provider connection. See the inner exception for details.
System.InvalidOperationException: 已有打开的与此 Command 相关联的 DataReader，必须首先将它关闭。

查询了资料  https://www.cnblogs.com/dongshuangjie/p/4832100.html

发现犯了个 低级错误，

千万不要在Iqueryable查询句子里面嵌套saveChange。  Iqueryable与Ilist的区别不再啰嗦。