Entity Framework 6 - Knowledge Base (KB)

MusicStore 'System.Data.Objects.ObjectSet<....>' does not contain a definition for 'Add' and no extension method 'Add' accepting a first argument

I'm following the MusicStore tutorial I'm already on the ...Part 8 of the tutoria...l. I got this error when I tried to add the ShoppingCart class.. I tried to google for a possible solution but failed to find a clean one T_T .. based on my research I'm ...