After downloading the EF6 by nuget and try to run my project, it returns the following error:
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=260882 for more information.
I just got into the same problem and it looks like EntityFramework although installed from NuGet Package Manager was not correctly installed in the project.
I managed to fix it by running the following command on Package Manager Console:
PM> Install-Package EntityFramework
You've added EF to a class library project. You also need to add it to the project that references it (your console app, website or whatever).