No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'. Make sure the provider is registered in the 'entityFramework' section of the application config

项目分层，EntityFramework层引入了EntityFramework包，Service层引用了 EntityFramework层，写了一些service类， 在Web层调用Service层的service类进行数据访问操作，结果报错：
No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'. Make sure the provider is registered in the 'entityFramework' section of the application config file. See http://go.microsoft.com/fwlink/?LinkId=26088

经多方查找，发现除了EntityFramework层引入EntityFramework包之外，在Web层也要引入EntityFramework包。问题解决。

解决方案地址：
https://blog.csdn.net/laokaizzz/article/details/22506311?locationNum=8