EF "There is already an open DataReader associated with this Command which must be closed first."

1.出现问题

场景1：在插入数据之前，先进行判断是否存在

执行SqlDataReader.Read之后，如果还想用另一个SqlCommand执行Insert或者Update操作的话，

会得到一个错误提示：There is already an open DataReader associated with this Command which must be closed first.

2.解决方法

在ConnectionString中加上一个参数“MultipleActiveResultSets”, 将其值设置为true。

MultipleActiveResultSets可以使数据库连接复用。这样就不怕数据库的连接资源被耗尽了。使用方法很简单，只需要把它加到数据的连接字符串中即可。

例如:server=(local);Integrated Security = true;database=AdventureWorks;MultipleActiveResultSets=true;

EF "There is already an open DataReader associated with this Command which must be closed first."

原文：http://www.cnblogs.com/xcsn/p/6307592.html