Error: No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'

Question

I recently upgraded/updated Entity Framework in an old project from version 4 or 5 to version 6. Now I get this exception:

An exception of type \'Syst

Answer 1

Ok, this is pretty weird. I have a couple of projects: one is a UI project (an ASP.NET MVC project) and the others are projects for stuff like repositories. The repositories project had a reference to EF, but the UI project didn't (because it didn't need one, it just needed to reference the other projects). After I installed EF for the UI project as well, everything started working. This is why, it added this piece of code to my Web.config: