I have 2 projects in my solution, I have a project with Entity Framework Core installed:
And in the other ASP.NET Web API project I have these packages:
I got this error because Visual Studio defaulted to using entity framework core rather than old-school entityframework for .NET Framework: entity framework 6. This was my solution:
EntityFramework\Update-Database
Or reference the version explicitly:
EntityFramework6\Update-Database
Also worth checking the right project is selected in the Package Manager Console. That likes to sneak back to other projects half the time!