AutoMapper in Infrastructure project and error 'Missing type map configuration'

Question

I have all my db entities in Infrastructure project (important: it's db-first approach). My dto entities are located in Application project. What I want to do is to map Db entities to Dto entities but when I do so I get an error:

AutoMapper.AutoMapperMappingException: Missing type map configuration or unsupported mapping. Mapping types: List 1 -> UserDto System.Collections.Generic.List`1[[RegionManagement.Persistence.ModelsDb.User, RegionManagement.Persistence, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]] -> RegionManagement.Domain.Entities.Administration.UserEntries.UserDto

At the first glance everything looks ok and I wonder where the problem lies.

I do the mapping in 2 places in my app: in Infrastructure project (db entity -> dto entity) and Application project (dto entity -> other dto/vm entities). Everything worked fine until I added mapping in Infrastucture. So basically I have db entity User and dto entity UserDto. I created a repository in Infrastructure project where I map those entities and mapping profile in seperate class:

UserRepository.cs

    public class UserRepository : IUserRepository<UserDto>
    {
        protected readonly RegionManagementDbContext _dbContext;
        private readonly IMapper _mapper;

        public UserRepository(RegionManagementDbContext dbContext, IMapper mapper)
        {
            _dbContext = dbContext;
            _mapper = mapper;
        }

        public async Task<IReadOnlyList<UserDto>> ListAllAsync()
        {
            var dbDataList = await _dbContext.Users.ToListAsync();
            var mapList = _mapper.Map<UserDto>(dbDataList);
            return (IReadOnlyList<UserDto>)mapList;
        }
    }

MappingProfile.cs

    public class MappingProfile : Profile
    {
        public MappingProfile()
        {
            CreateMap<User, UserDto>();
        }
    }

and the I register service as an extension of IServiceCollection (I still do it in Infrastructure project), as shown below:

InfrastructureServiceRegistration.cs

    public static class InfrastructureServiceRegistration
    {
        public static IServiceCollection AddPersistenceServices(this IServiceCollection services, IConfiguration configuration)
        {
            services.AddDbContext<RegionManagementDbContext>(options =>
                options.UseSqlServer(configuration.GetConnectionString("RegionManagementConnectionString")));

            services.AddAutoMapper(Assembly.GetExecutingAssembly());
            services.AddScoped<IUserRepository<UserDto>, UserRepository>();

            return services;
        }
    }

Startup.cs (AddApplicationServices is where I registered AutoMapper for Application project):

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddApplicationServices();
            services.AddInfrastructureServices(Configuration);
            services.AddControllers();

            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "RegionManagement.Api", Version = "v1" });
            });

        }

Error indicates that something is wrong with mapping User -> UserDto but have no idea what it could be.

I scan assembly for profiles in this place: services.AddAutoMapper(Assembly.GetExecutingAssembly()); but it doesn't help.

Answer 1

Error

Missing type map configuration or unsupported mapping. Mapping types: List 1 -> UserDto

says that you're trying to map a List into a UserDto.

This is the line with the problem:

var mapList = _mapper.Map<UserDto>(dbDataList);

Try to rewrite it this way:

var mapList = dbDataList.Select(_mapper.Map<UserDto>)