AutoMapping from a different source collection type

Question

Given the classes below, I need to establish the mapping from Person to PersonDTO. The problem I am having is that PersonDTO's address field mapping did not occur.

public class Address
{
    public int Id { get; set; }
    public string Value { get; set; }
}

public class RegisteredAddresses
{
    public int Id { get; set; }
    public List<Address> Addresses { get; set; }

    public RegisteredAddresses()
    {
        this.Addresses = new List<Address>(); 
    }
}

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<RegisteredAddresses> AddressGroups { get; set; }

    public Person()
    {
        this.AddressGroups = new List<RegisteredAddresses>();
    }
}

public class PersonDTO
{
    public string Name { get; set; }
    public List<Address> Addresses { get; set; }

    public PersonDTO()
    {
        this.Addresses = new List<Address>();
    }
}

class Program
{
    static void Main(string[] args)
    {
        RegisteredAddresses registeredAddresses1 = new RegisteredAddresses();
        RegisteredAddresses registeredAddresses2 = new RegisteredAddresses();
        Person person = new Person();

        registeredAddresses1.Addresses.Add(new Address { Id = 1, Value = "address 1" });
        registeredAddresses1.Addresses.Add(new Address { Id = 2, Value = "address 2" });
        registeredAddresses1.Addresses.Add(new Address { Id = 3, Value = "address 3" });
        registeredAddresses1.Addresses.Add(new Address { Id = 4, Value = "address 4" });
        registeredAddresses1.Addresses.Add(new Address { Id = 5, Value = "address 5" });

        registeredAddresses2.Addresses.Add(new Address { Id = 1, Value = "address A" });
        registeredAddresses2.Addresses.Add(new Address { Id = 2, Value = "address B" });
        registeredAddresses2.Addresses.Add(new Address { Id = 3, Value = "address C" });
        registeredAddresses2.Addresses.Add(new Address { Id = 4, Value = "address D" });
        registeredAddresses2.Addresses.Add(new Address { Id = 5, Value = "address E" });

        person.Name = "person 1";
        person.AddressGroups.Add(registeredAddresses1);
        person.AddressGroups.Add(registeredAddresses2);

        Mapper.CreateMap<Person, PersonDTO>();

        // after this line....
        var personDto = Mapper.Map<Person, PersonDTO>(person);

        // .... personDTO.Addresses.Count() is zero; where it should be 10

    }
}

Answer 1

You need to tell AutoMapper how to map from the addresses contained in the AddressGroups to the addresses in PersonDTO. Something like:

Mapper.CreateMap<Person, PersonDTO>()
      .ForMember(pd => pd.Addresses,
                 opt => opt.ResolveUsing(p => p.AddressGroups
                                               .SelectMany(ra => ra.Addresses)
                                        )
                );