AutoMapper not detecting profiles in external assemblies

Question

I am using ASP.Net core with latest Automapper. This is related to this and this. I think I am doing what needs to be done according to those questions, but still I get below error from Automapper.

AutoMapper.AutoMapperMappingException: Missing type map configuration or unsupported mapping.
Mapping types:
ToDoDto -> CreateTodoCommand
Module.Todo.Domain.Dto.ToDoDto -> Module.Todo.Domain.Commands.CreateTodoCommand
at lambda_method19(Closure , ToDoDto , CreateTodoCommand , ResolutionContext )

I have an interface which will be implemented by classes that needs to participate in mappings.

public interface IMapFrom<T>
{
    void Mapping(Profile profile) => profile.CreateMap(typeof(T), GetType());
}

But mapping classes can be in many assemblies since I have a plugin architecture. So, lot of stuff are being loaded dynamically by the host application. My Assembly locating method use below line to load Assembly in a loop until it finishes loading all modules.

AssemblyLoadContext.Default.LoadFromAssemblyPath(file.FullName); //file.FullName is full path to Dll like E:\Project\Modules\Module.Todo\bin\Module.Todo.dll

Once it's done I can see loaded assemblies in watch window

Above loading method gets called in ConfigureServices(). I know this should work because the same assembly collection is passed to MediatR services.AddMediatR(assemblies) as well as Automapper services.AddAutoMapper(assemblies);

MediatR scans and find all Commands etc. but Automapper fails to locate mappings from other assemblies. However Automapper loads profiles properly from directly linked assemblies via Assembly.GetExecutingAssembly().GetReferencedAssemblies()

What may be the problem?

If you explicitly pass the assemblies, everything will work. That rules out AM. Then you have your own code to check. — Lucian Bargaoanu, Jan 12 '21 at 10:06
Then I am wondering why MediatR works while Automapper doesn't. Same collection I am passing to both. — user2058413, Jan 12 '21 at 10:12
Both libraries have SourceLink enabled, so if you think it's worth the trouble, you can always debug and find out. — Lucian Bargaoanu, Jan 12 '21 at 10:25

score 0 · Answer 1 · answered Jan 14 '21 at 12:00

I got my assemblies to load properly and setup the mappings to work by making my mappings by inheriting Profile class like

public class MyProfile:Profile
{
    public MyProfile()
    {
        CreateMap<A,B>();
    }
}

and not using

public interface IMapFrom<T>
{
    void Mapping(Profile profile) => profile.CreateMap(typeof(T), GetType());
}

AutoMapper not detecting profiles in external assemblies

1 Answers1