使用Automapper的EF Core多对多返回API资源上的循环

Question

I'm using .net Core with EF2 and I want to setup this Many to Many relationship. Any Doctor can have many Appointments and vice versa. Also I want to implement Automapper mapping on top.

High Level Model Structure

**Doctor**
 - Id
 - Name
 - Appointments

**Appointment**
 - Id
 - Name
 - Category
 - Doctors

Doctors Model

[Table("Doctors")]
public class Doctor
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<DoctorAppointment> Appointments { get; set; }
    public Doctor()
    {
        Appointments = new Collection<DoctorAppointment>();
    }
}

Appointments Model

[Table("Appointments")]
public class Appointment
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Category { get; set; }
    public ICollection<DoctorAppointment> Doctors { get; set; }
    public Appointment()
    {
        Doctors = new Collection<DoctorAppointment>();
    }
}

Many to Many Doctors-Appointments Linking Table

[Table("DoctorAppointments")]
public class DoctorAppointment
{
    public int DoctorId { get; set; }
    public int AppointmentId { get; set; }
    public Doctor Doctor { get; set; }
    public Appointment Appointment { get; set; }  
}

DB context

public class MyDocDbContext : DbContext
{
    public DbSet<Appointment> Appointments { get; set; }
    public DbSet<Doctor> Doctors { get; set; }

    public MyDocDbContext(DbContextOptions<MyDocDbContext> options) 
      : base(options)
    {
    }
    protected override void OnModelCreating(ModelBuilder modelBuilder) 
    {
        modelBuilder.Entity<DoctorAppointment>().HasKey(da => 
          new { da.DoctorId, da.AppointmentId });

        modelBuilder.Entity<DoctorAppointment>()
            .HasOne(da => da.Doctor)
            .WithMany(p => p.Appointments)
            .HasForeignKey(pt => pt.DoctorId);

        modelBuilder.Entity<DoctorAppointment>()
            .HasOne(pt => pt.Appointment)
            .WithMany(t => t.Doctors)
            .HasForeignKey(pt => pt.AppointmentId);
    }
}

Doctors and Appointment Controllers :

    [HttpGet("appointment/{id}")]
    public async Task<IActionResult> GetAppointment(int id)
    {
        var app =  await context.Appointments
          .Include(a => a.Doctors)
          .ThenInclude(da => da.Doctor)        
          .SingleOrDefaultAsync(a => a.Id == id);
        return Ok(app);
    }

    [HttpGet("doctor/{id}")]
    public async Task<IActionResult> GetDoctor(int id)
    {
      var doc =  await context.Doctors   
        .Include(d => d.Appointments)
        .ThenInclude(da => da.Appointment)
        .SingleOrDefaultAsync(v => v.Id == id);
        return Ok(doc);
    }

Now implementing Automapper Resource Mapping ...

Until this point everything works fine, as when fetching on of those two entities it returns all the relations. The problem comes when using Automapper to map the Domain to API Resource. Using the following mapping resources:

DoctorResource

public class DoctorResource
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<AppointmentResource> Appointments { get; set; }
    public DoctorResource()
    {
        Appointments = new Collection<AppointmentResource>();
    }
}

AppointmentResource

public class AppointmentResource
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Category { get; set; }
    public ICollection<DoctorResource> Doctors { get; set; }
    public AppointmentResource()
    {
        Doctors = new Collection<DoctorResource>();
    }

}

Finally, the mapping is the following:

public class MappingProfile : Profile
{
    public MappingProfile()
    {
        // Domain to API Resource

        CreateMap<Doctor, DoctorResource>()
             .ForMember(dr => dr.Appointments, opt => opt
                 .MapFrom(d => d.Appointments
                 .Select(y => y.Appointment)
                 .ToList()));

        CreateMap<Appointment, AppointmentResource>()
            .ForMember(dr => dr.Doctors, opt => opt
                .MapFrom(d => d.Doctors
                .Select(y => y.Doctor)
                .ToList()));
    }
}

So, when NOT using the mapping resources, the JSON result is this (the wanted one):

**http://localhost:5000/api/appointment/1**

{
"id": 1,
"name": "Personal Trainer",
"category": "Fitness",
"doctors": [
    {
        "doctorId": 2027,
        "appointmentId": 1,
        "doctor": {
            "id": 2027,
            "name": "Dr. Cunha",
            "appointments": [],
        }
    },
    {
        "doctorId": 2028,
        "appointmentId": 1,
        "doctor": {
            "id": 2028,
            "name": "Dr. Gouveia",
            "appointments": [],
        }
    },
    {
        "doctorId": 2029,
        "appointmentId": 1,
        "doctor": {
            "id": 2029,
            "name": "Dr. Tiago",
            "appointments": [],
        }
    }
  ]
}

However when using Automapper to map the API response it expands the Appointments category and the the Doctors again, and so on...

**http://localhost:5000/api/appointment/1**

{
"id": 1,
"name": "Personal Trainer",
"category": "Fitness",
"doctors": [
    {
        "id": 2027,
        "name": "Dr. Cunha",
        "appointments": [
            {
                "id": 1,
                "name": "Personal Trainer",
                "category": "Fitness",
                "doctors": [
                    {
                        "id": 2028,
                        "name": "Dr. Gouveia",
                        "appointments": [
                            {
                                "id": 1,
                                "name": "Personal Trainer",
                                "category": "Fitness",
                                "doctors": [
                                     { ....
                                      and so on...

However for some unknown reason to me the Doctor Controller returns the desired output.

Sorry about the lengthy post, but I couldn't provide you with a clear picture without exposing the whole thing.

Cheers

Answer 1

I assume that you'r MappingProfile should be change like bellow:

public MappingProfile()
{
    // Domain to API Resource

    CreateMap<Doctor, DoctorResource>()
         .ForMember(dr => dr.Appointments, opt => opt
             .MapFrom(d => d.DoctorAppointment
             .Select(y => y.Appointment)
             .ToList()));

    CreateMap<Appointment, AppointmentResource>()
        .ForMember(dr => dr.Doctors, opt => opt
            .MapFrom(d => d.DoctorAppointment
            .Select(y => y.Doctor)
            .ToList()));
}

Instead of MapFrom(d => d.Doctors) and also MapFrom(d => d.Appointments) replace them with MapFrom(d => d.DoctorAppointment)

it should be work.