Scaffolding doesn't work when DbContext is in a separate project

[majid-joghataey]

There was an error running selected code generator:

An unhandled exception occurred while processing the request.
InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNetCore.Identity.SignInManager`1[Microsoft.AspNetCore.Identity.IdentityUser]' while attempting to activate 'WebUI.Areas.Identity.Pages.Account.LoginModel'.

I've found others that have had similar issues a few months back, but no-one had any solutions other then bringing everything into the same project.

Has anyone encountered this and found a solution?