使用Automapper进行多对多到DTO的转换。

Question

如果我在EF中定义了多对多的关系。

public class StudentImage 
{
    public int StudentId { get; set; }
    public int ImageId { get; set; }
    public int Order { get; set; }
    public virtual Student Student { get; set; }
    public virtual Image Image { get; set; }
}

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<StudentImage> Images { get; set; }
}


public class Image
{
    public int Id { get; set; }
    public string Filename { get; set; }
    public virtual ICollection<StudentImage> Students { get; set; }
}

和DTO的关系。

 public class ImageDTO
    {
        public int Id { get; set; }
        public string Filename { get; set; }
        public int Order { get; set; }
    }

    public class StudentIDO
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public ICollection<ImageDTO> Images { get; set; }
    }

我怎么能用Automapper从学生映射到学生DTO，从图像映射到图像DTO？

Answer 1

映射

Mapper.CreateMap<Student, StudentIDO>();

Mapper.CreateMap<StudentImage, ImageDTO>()
        .ForMember(d => d.Id, opt => opt.MapFrom(s => s.ImageId))
        .ForMember(d => d.Filename, opt => opt.MapFrom(s => s.Image.Filename));

Mapper.CreateMap<StudentIDO, Student>()
      .AfterMap((s, d) =>
      {
          foreach (var studentImage in d.Images)
              studentImage.StudentId = s.Id;
      });

Mapper.CreateMap<ImageDTO, StudentImage>()
      .ForMember(d => d.ImageId, opt => opt.MapFrom(s => s.Id));

使用方法

var studentDTO = Mapper.Map<StudentIDO>(student);
var student = Mapper.Map<Student>(studentDTO);

Answer 2

所以Image和ImageDTO是1:1的关系，这很容易被AutoMappper映射。

Mapper.CreateMap<Image, ImageDTO>();

Mapper.CreateMap();最后一个Student和StudentDTO，他们有包含列表。

Mapper.CreateMap<Student,StudentDTO>
.ForMember(s => s.Images, opt=>opt.MapFrom(p=>p.Images));

有时如果你尝试这样做，它的性能并不好。