How to map from nested list to destination object with automapper?

Question

I have a source object like so:

public class ParentDto
{
    public List<EntityDto> EntityDtos { get; set; }
    // some other stuff...
}

and a destination object like so:

public class SomeModel
{
    [Key]
    public Guid Id { get; set; }
    public Entity Entity { get; set; }
}

In a different part of my application I already map my EntityDto to my Entity by using Profiles:

CreateMap<EntityDto, Entity>()
            .ForMember(dest => dest.Member,
                opt => opt.MapFrom(src => DoSomeStuff(src.AnotherMember)))
            .ForMember(dest => dest.YetAnotherMember,
                opt => opt.MapFrom(src => DoSomeOtherStuff(src.Whatever)));

Is it possible to reuse this map in order to also map my parent object Dto, which includes a list of entityDtos?

CreateMap<ParentDto, SomeModel>()
            .ForMember(dest => dest.Id,
                opt => opt.Ignore())

            // some more stuff...

            // This is where I am struggling!
            .ForMember(dest => dest. Entity,
                opt => opt.MapFrom(src => src.EntityDtos[0]));

How would I address the fact that I have already a mapping for EntityDto to Entity and the fact that I have to deal with the list?

Answer 1

One has nothing to do with the other. The mappings you define are utilized based on the types of the object(s) that are fed into it and/or the generic type param(s) specified. In other words, something like _mapper.Map<SomeModel>(parentDto) will use the CreateMap<ParentDto, SomeModel> definition, while _mapper.Map<Entity>(entityDto) would use the CreateMap<EntityDto, Entity> definition.

Now, when AutoMapper gets to mapping the collection property, it will by default use the definition for EntityDTO->Entity mapping, but if you specify a custom mapping via MapFrom, for example, then that will take precedence.