C# project layer structure - where do mappers fit in

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C#

.NET-Core

I'm trying to set up a layered structure for a Blazor-server application, but seem to be keep getting confused on where classes should reside to keep dependencies loosely coupled. In a lot of examples I see projects called 'Core' and 'Services', but never is there an explanation of what sort of classes should be in these projects.

The structure I have seemed fine, until I realized that the UI needs a reference to both the business layer (for the service injection) and a reference to the DAL for the viewmodel to model mapping. Surely this is not the best way to do this?
Also, should my concrete classes reside in the same layer as the interfaces they are implementing?

Any advice please.

What I have tried:

So far i have the following structure:

DataAccess (project)
 - DAL (folder) Has classes and interfaces for each entity to wrap entity framework CRUD operations
 - Models (folder) Has model classes and DBsets generated by entity framework

Business(project)
 - Services (folder) Has classes and interfaces that make calls to the DAL project, performs some additional logic and return models. Also has classes that have tasks that are not dependent on the data source.

BlazorUI (project)
 - Pages (folder) Has razor components with injected services from the business project.
 - ViewModels (folder) Poco classes with data annotations.
 - Mappers (folder) Classes to convert a ViewModel to a DataAccess.Model and vice versa.