使用 Automapper - 如何从此 ICollection 映射？

Question

I am using entity framework and automapper for the first time. I am lost. I have a class containing an ICollection of another class which I wish to map:

Here are my classes:

public class BaseEntity {
    public int Id { get; set; }
}

public class Car : BaseEntity {
    public string Make { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }
    public ICollection<CarPart> CarParts { get; set; }
}

public class Part : BaseEntity {
    public string PartName { get; set; }
}

public class CarPart : BaseEntity {
    public int CarId { get; set; }
    public Car Car { get; set; }
    public int PartId { get; set; }
    public Part Part { get; set; }
}

and then my DTO:

public class CarDTO {
    public int Id { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }
    public ICollection<CarPart> CarParts { get; set; }
}

and my mapping configuration profile contains:

CreateMap<Car, CarDTO> ();

and then in my controller I use:

private readonly IMapper _mapper;
return _mapper.Map<Car, CarDTO>(car);

When I hit the API I get the following error:

Destination Member:
CarParts
 ---> AutoMapper.AutoMapperMappingException: Missing type map configuration or unsupported mapping.
Mapping types:
CarPart -> Part
Entities.CarPart -> Entities.Part

What changes do I need to make to fix this? Thank-you.

Edit: The following is all in StartUp.cs:

public void ConfigureServices(IServiceCollection services)
{
     services.AddAutoMapper(typeof(MappingProfiles));
}

Edit #2: Changing the scope of this a little bit. I changed CarDTO to

public class CarDTO {
    public int CarId { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }
    public IReadOnlyList<Part> Parts { get; set; }
}

and added the following DTO:

 public class PartDTO
    {
        public int PartId { get; set; }
        public string PartName { get; set; }
    }

and edited my mapping configuration profile to

  public MappingProfiles () {
    
            CreateMap<Car, CarDTO> ()
.ForMember(dest => dest.CarId, opt => opt.MapFrom(src => src.Id))
                .ForMember (dest => dest.Parts, opt =>
                    opt.MapFrom (src => src.CarParts.Select (x => x.Part
                    )));
    
            CreateMap<Part, PartDTO>()
            .ForMember(dest => dest.PartId, opt => opt.MapFrom(src => src.Id))
        }

which returns this:

{
    "carId": 8,
    "make": "some make",
    "model": "some model",
    "year": 2001,
    "parts": [
        {
            "partName": "Fully sick Wheels",
            "id": 3
        },
        {
            "partName": "Mad Engine",
            "id": 4
        }
    ]
}

How can I change this to:

{
    "carId": 8,
    "make": "some make",
    "model": "some model",
    "year": 2001,
    "parts": [
        {
            "partName": "Fully sick Wheels",
            "partId": 3
        },
        {
            "partName": "Mad Engine",
            "partId": 4
        }
    ]
}

Answer 1

Change the collection property in your CarDTO so that it becomes -

public class CarDTO 
{
    public int CarId { get; set; }
    public string Make { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }
    public IReadOnlyList<PartDTO> Parts { get; set; }   // this one
}

Just change it from IReadOnlyList<Part> to IReadOnlyList<PartDTO> That should solve your problem.

With your current definition of CarDTO , the following configuration in your first map -

.ForMember (dest => dest.Parts, opt =>
                    opt.MapFrom (src => src.CarParts.Select (x => x.Part)));

is basically mapping from Part to Part .

So your second map, from Part to PartDTO , is not being used at all. Hence PartId is not showing up.

Answer 2

那应该工作。

CreateMap<Car, CarDTO>().ReverseMap();

Answer 3

Add also

CreateMap<CarPart, CarPart> ();
CreateMap<Part, Part> ();