Why does the model return null after using Automapper?

Question

To model Endereco returns null after mapping (Automapper), why ?

Example:

  using AutoMapper;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AutoMapperDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            InitializeAutomapper();

            Cliente cliente = new Cliente()
            {
                ClienteID = 1,
                Nome = "João da Silva",
                CPF = "111.888.999-99"
            };

            Endereco end1 = new Endereco();
            end1.EnderecoID = 1;
            end1.ClienteID = 1;
            end1.Logradouro = "Rua XV de Novembro, 151";
            end1.CEP = "01000-000";
            cliente.Endereco.Add(end1);

            Endereco end2 = new Endereco();
            end2.EnderecoID = 2;
            end2.ClienteID = 1;
            end2.Logradouro = "Av. Interlagos, 1200";
            end2.CEP = "03450-000";
            cliente.Endereco.Add(end2);

            var clienteDTO = Mapper.Map<Cliente, ClienteDTO>(cliente);

            Console.WriteLine("Cliente ID::" + clienteDTO.ClienteID + ", Nome: " + clienteDTO.Nome + ", CPF: " + clienteDTO.CPF);
            Console.WriteLine("Endereço Cliente 1 ID:" + clienteDTO.EnderecoDTO[0].EnderecoID + ", Logradouro: " + clienteDTO.EnderecoDTO[0].Logradouro + ", CEP: " + clienteDTO.EnderecoDTO[0].CEP);
            Console.WriteLine("Endereço Cliente 2 ID:" + clienteDTO.EnderecoDTO[1].EnderecoID + ", Logradouro: " + clienteDTO.EnderecoDTO[1].Logradouro + ", CEP: " + clienteDTO.EnderecoDTO[1].CEP);
            Console.ReadLine();
        }
        static void InitializeAutomapper()
        {
            Mapper.Initialize(cfg =>
            {
                cfg.CreateMap<Cliente, ClienteDTO>();
                cfg.CreateMap<Endereco, EnderecoDTO>();
            });
        }
    }

    public class Cliente
    {
        public Cliente()
        {
            Endereco = new List<Endereco>();
        }
        public int ClienteID { get; set; }
        public string Nome { get; set; }
        public string CPF { get; set; }
        public List<Endereco> Endereco { get; set; }
    }
    public class Endereco
    {
        public int EnderecoID { get; set; }
        public int ClienteID { get; set; }
        public string Logradouro { get; set; }
        public string   CEP { get; set; }
        public Cliente Cliente { get; set; }
    }

    public class ClienteDTO
    {
        public int ClienteID { get; set; }
        public string Nome { get; set; }
        public string CPF { get; set; }
        public List<EnderecoDTO> EnderecoDTO { get; set; }
    }

    public class EnderecoDTO
    {
        public int EnderecoID { get; set; }
        public int ClienteID { get; set; }
        public string Logradouro { get; set; }
        public string CEP { get; set; }
        public ClienteDTO ClienteDTO { get; set; }
    }
}

Answer 1

It was not mapping correctness because, although it had been defined the mapper for address types (cfg.CreateMap<Endereco, EnderecoDTO>();), in class Cliente, the property is a List<Endereco>.

That’s why it’s important to inform Automapper how to correctly map the property Endereco, being like this:

Mapper.Initialize(cfg =>
            {
                cfg.CreateMap<Cliente, ClienteDTO>()
                   .ForMember(s => s.EnderecoDTO, c => c.MapFrom(m => m.Endereco));
                cfg.CreateMap<Endereco, EnderecoDTO>();
            });

Thus the Automapper knows how to map the type Endereco for EnderecoDTO and also knows that the member EnderecoDTO class ClienteDTO will be mapped from the member Endereco class Cliente.

Just one comment: as they are lists, I suggest using the property name in the plural, which also helps to distinguish from the class name:

public List<Endereco> Enderecos { get; set; }

and

public List<EnderecoDTO> EnderecosDTO { get; set; }