AutoMapper - Map Many-to-Many Relationships

Question

In my DAL, I have the following models establishing a many-to-many relationship.

public class FamilyMember
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public ICollection<FamilyMemberPhone> FamilyMemberPhones { get; set; }
}
public class FamilyMemberPhone
{
    public int FamilyMemberId { get; set; }
    public int PhoneId { get; set; }
    public FamilyMember FamilyMember { get; set; }
    public Phone Phone { get; set; }
}
public class Phone : AuditableEntity
{
    public int Id { get; set; }
    public string PhoneNumber { get; set; }
    public bool IsPreferred { get; set; }
    public ICollection<FamilyMemberPhone> FamilyMemberPhones { get; set; }
}

In my DTO, I have the following classes

public class FamilyMemberDto 
{
    public int Id { get; set; }
    public int FamilyId { get; set; }
    [Required]
    public string FirstName { get; set; }
    [Required]
    public string LastName { get; set; }
    public bool IsPrimary { get; set; }
    [Required]
    public List<Phone> FamilyMemberPhones { get; set; }
    public string FullName => $" {FirstName} {LastName}";
}
public class PhoneDto
{
    public int Id { get; set; }
    public string PhoneNumber { get; set; }
    public bool IsPreferred { get; set; }
    public PhoneType PhoneType { get; set; }
}

My Mapping configuration looks like this:

CreateMap<Dal.Models.Phone, Dto.PhoneDto>().ReverseMap().IgnoreAuditableFields();

CreateMap<Dal.Models.FamilyMember, Dto.FamilyMemberDto>();

CreateMap<Dal.Models.FamilyMemberPhone, Dto.PhoneDto>()
            .ForMember(d => d.Id, opt => opt.MapFrom(s => s.Id))
            .ForMember(d => d.PhoneNumber, opt => opt.MapFrom(s => s.Phone.PhoneNumber))
            .ForMember(d => d.PhoneType, opt => opt.MapFrom(s => s.Phone.PhoneType));

CreateMap<Dto.FamilyMemberDto, Dal.Models.FamilyMember>()
            .AfterMap((s, d) =>
            {
                if (d.FamilyMemberPhones != null)
                    foreach (var fmp in d.FamilyMemberPhones)
                        fmp.Id = s.Id;
            });

CreateMap<Dto.PhoneDto, Dal.Models.FamilyMemberPhone>()
            .ForMember(d => d.PhoneId, opt => opt.MapFrom(s => s.Id));

My Unit Test looks like this:

var member = new Bll.Dto.FamilyMemberDto
        {
            FamilyId = 12,
            FirstName = "Jane",
            LastName = "Doe",
            BirthDate = DateTime.Parse("11-01-1990"),
            Email = "test@test.com",
            FamilyMemberPhones = new List<Bll.Dto.PhoneDto>
            {
                new Bll.Dto.PhoneDto
                {
                    PhoneNumber = "test",
                    IsPreferred = true,
                },
                new Bll.Dto.Phone
                {
                    PhoneNumber = "hello",
                    IsPreferred = false,
                }
            }
        };
        await Manager.Save(member);

When I'm trying to map the DTO to Model using Mapper.Map<Dal.Models.FamilyMember>(dto) , in the entity.FamilyMemberPhones object, I see two items in the collection. However, digging deeper into the collection, all Dal.Models.Phone properties are null.

What am I doing wrong?

Answer 1

From this area of your code

CreateMap<Dto.FamilyMemberDto, Dal.Models.FamilyMember>()
            .AfterMap((s, d) =>
            {
                if (d.FamilyMemberPhones != null)
                    foreach (var fmp in d.FamilyMemberPhones)
                        fmp.Id = s.Id;
            });

You are assigning a value to a variable created in a loop. That is fmp.Id = s.Id; maybe instead of s.Id = fmp.Id; or even something else. Because that doesn't look like you're doing anything there.

Answer 2

@formula12's answer sparked a thought in my head. I need to account for every phone number that is being added to a family member. As the result, every time I am mapping FamilyMemberDto to FamilyMember , I need to also account for list of Phone inside of the map.

This is my new mapping profile:

CreateMap<Phone, Dto.PhoneDto>().ReverseMap().IgnoreAuditableFields();
        CreateMap<FamilyMember, Dto.FamilyMemberDto>();
        CreateMap<FamilyMemberPhone, Dto.PhoneDto>()
            .ForMember(d => d.Id, opt => opt.MapFrom(s => s.Id))
            .ForMember(d => d.PhoneNumber, opt => opt.MapFrom(s => s.Phone.PhoneNumber))
            .ForMember(d => d.PhoneType, opt => opt.MapFrom(s => s.Phone.PhoneType));
        CreateMap<Dto.FamilyMemberDto, FamilyMember>()
            .AfterMap((s, d) =>
            {
                var memberPhones = new List<FamilyMemberPhone>();                    
                foreach (var fmp in s.FamilyMemberPhones)
                {
                    var phone = new FamilyMemberPhone
                    {
                        Phone = new Phone
                        {
                            Id = fmp.Id,
                            PhoneNumber = fmp.PhoneNumber,
                            PhoneType = fmp.PhoneType
                        }
                    };
                    memberPhones.Add(phone);
                }
                d.FamilyMemberPhones = memberPhones;
            });
        CreateMap<Dto.PhoneDto, FamilyMemberPhone>()
            .ForMember(d => d.PhoneId, opt => opt.MapFrom(s => s.Id));

Used case: Let's say my family member has three (3) items in FaimlyMemberDto.FamilyMemberPhones which is a List<PhoneDto> , when going through the mapping process, My entity now has 3 FamilyMemberPhone objects in the ICollection<FamilyMemberPhones> in FamilyMember object. Inside of each of those, there is now a Phone object that maps to PhoneDto .