异常：The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information.
方法1
网上找到这样一个方法，在代码中添加：
public void FixEfProviderServicesProblem()
{
//The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer'
//for the 'System.Data.SqlClient' ADO.NET provider could not be loaded.
//Make sure the provider assembly is available to the running application.
//See http://go.microsoft.com/fwlink/?LinkId=260882 for more information.
var instance = System.Data.Entity.SqlServer.SqlProviderServices.Instance;
}
本段代码并未使用；至于为什么会消除异常，还待深入了解。但这不是一个好的解决方法，它可能会引起另外一些问题。
方法2
在配置有Entity Framework的子项目中，有几个DLL如下：
出现异常的原因主要是缺少了EntityFramework.DynamicFilters.dll、EntityFramework.SqlServer.dll、EntityFramework.SqlServer.xml。将这三个文件拷贝到主项目中，即可。