Question

I’m starting to use AutoMapper and some doubts arose.
Where is the correct way to map a dto into a domain model?
I’m doing this:

DTO:

public class PersonInsert
{
    [Required]
    public string Name { get; set; }
    public string LastName { get; set; }
}

Action:

[HttpPost]
public ActionResult Insert(PersonInsert personInsert)
{
    if (ModelState.IsValid)
    {
        new PersonService().Insert(personInsert);

        return RedirectToAction("Insert");
    }

    return View("Insert");
}

Service:

public class PersonService
{
    public int Insert(PersonInsert personInsert)
    {
        var person = Mapper.Map<PersonInsert, Person>(personInsert);

        return new PersonRepository().Insert(person);
    }
}

Repository:

 public class PersonRepository
    {
        internal int Insert(Person person)
        {
            _db.Person.Add(person);
            _db.SaveChanges();

            return person.Id;
        }
     }

So, is this correct? should my service knows about domain? or should I make the bind in repository only? is correct to use [Required] in DTO?

Answer 1

Is this correct?

I personally don’t see anything wrong with having your service do the mapping

Is it correct to use [Required] in DTO

No, DTOs should have no business logic whatsoever. They should be used purely for transmitting data across different tiers/layers of your application.

DataAnnotations are typically used on ViewModels for client/server side validation, therefore, I would add another separation into your model and introduce a ViewModel for your Insert action e.g.

public class PersonViewModel    
{
    [Required]
    public string Name { get; set; }
    public string LastName { get; set; }
}

public class PersonDto
{
    public string Name { get; set; }
    public string LastName { get; set; }
}

Action:

[HttpPost]
public ActionResult Insert(PersonViewModel personViewModel)
{
     if (ModelState.IsValid)
     {
         var personDto = Mapper.Map<PersonViewModel, PersonDto>(personViewModel);
         new PersonService().Insert(personDto);
         ...
      }
      ...
     }
}

Service:

public class PersonService
{
    public int Insert(PersonDto personDto)
    {
        var person = Mapper.Map<PersonDto, Person>(personDto);

        return new PersonRepository().Insert(person);
    }
}

It may seem overkill in this scenario (considering the only difference is the [Required] attribute). However, in a typical MVC application you would want to ensure a clean separation between your ViewModels and your business models.