AddIdentity() fails “InvalidOperationException: Scheme already exists: Identity.Application”

Question

I\'m trying to add facebook login to my .NET Core 2.1 site

I\'m following this , guide and more specific, this (for facebook login)

After have adding the lines

Answer 1

I also had the same problem.

I found out that services.AddIdentity() in 2 places.

I removed one of them and now everything works as expected.