Automapper issue with identityserver4 - MissingMethodException: Method not found: '!!0 AutoMapper.IMapper.Map(System.Object)'

Do not move backward, Do not downgrade, Upgrade

It seems that the AutoMapper 10.0.0 has a bug, the solution to that problem was to upgrade AutoMapper to 10.1.1 version.

This version is very new, it released 4 days before the date of this answer.

Had the same issue after adding AutoMapper to another project. I was using the same versions. Identity 3.1.8

Automapper v10 and AutoMapper.Extensions.Microsoft.DependencyIn v8.0.1

I found the best solution for me is to rollback the Automapper version to 9 and the DI respectively.