Create mapping to the foreign key

debugcn Published at Dev

BAD_SEED

Suppose I have this Domain Model:

public class Department
{
    public int DepartmentId { get; set; }
    public String DepartmentName { get; set; }
    public ICollection<Course> Courses { get; set; }
}

public class Course
{
    public String CourseName { get; set; }
    public String CourseDescription { get; set; }
}

and a relative Persistence Model, optimized for Entity Framework and Code First database creation:

public class DepartmentDTO
{
    public int DepartmentId { get; set; }
    public String DepartmentName { get; set; }
    public ICollection<CourseDTO> Courses { get; set; }
}

public class CourseDTO
{
    public int CourseId { get; set; }
    public int DepartmentId { get; set; }
    public String CourseName { get; set; }
    public String CourseDescription { get; set; }
}

and then I have a test class, where I make all mapping using Automapper:

    static void Main(string[] args)
    {
        Department dep = CreateDepartment();

        Mapper.CreateMap<Department, DepartmentDTO>();
        Mapper.CreateMap<Course, CourseDTO>()
              .ForMember(dst => dst.CourseId, src => src.UseValue<int>(13)); // in my real scenario this is an autogenerated GUID

        DepartmentDTO depDTO = Mapper.Map<DepartmentDTO>(dep);
    }

    public static Department CreateDepartment()
    {
        ICollection<Course> listOfCourses = new List<Course>();
        listOfCourses.Add(new Course { CourseDescription = "A dummy course", CourseName = "Test Course" });
        return new Department { DepartmentId = 42, DepartmentName = "Test Department", Courses = listOfCourses };
    }

So far so good, the map is almost complete, and only one thing is missing: the CourseDTO.DepartmentId should be 42.

In this case everything is fine cause I can access to the value through dep.DepartmentId, but this is not the real scenario.

How can I configure AutoMapper to reach my goal?

Yuliam Chandra

You can create custom Resolver to set the DepartmentId for each Course when resolving Courses.

public class CourseResolver : ValueResolver<Department, ICollection<CourseDTO>>
{
    protected override ICollection<CourseDTO> ResolveCore(Department source)
    {
        var coursesDto = source.Courses
            .Select(c => Mapper.Map<CourseDTO>(c)).ToList();
        coursesDto.ForEach(c => c.DepartmentId = source.DepartmentId);
        return coursesDto;
    }
}

Configuration:

 Mapper.CreateMap<Department, DepartmentDTO>()
     .ForMember(obj => obj.Courses, opt => opt.ResolveUsing<CourseResolver>());
 Mapper.CreateMap<Course, CourseDTO>();

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