Simple Automapper Example

Question

I am having a hard time to understand how to map certain objects. Please answer some questions about this simple example.

Example code

class User {     private int id;     private string name; }  class Group {     private int id;     private string name;     private List<User> users; }  [DataContract] public class UserDto {     [DataMember]     public int id { get; set; }     [DataMember]     public string name{ get; set; }       }  [DataContract] public class GroupDto {     [DataMember]     public int id { get; set; }     [DataMember]     public string name{ get; set; }     [DataMember]     public List<User> Users { get; set; }       } 

The mappers

Mapper.CreateMap<User, UserDto>(); Mapper.CreateMap<UserDto, User>();  Mapper.CreateMap<Group, GroupDto>(); Mapper.CreateMap<GroupDto, Group>(); 

When mapping Group to GroupDto, do you have to map User to UserDto internally because the List<User> in Group consist of unmapped Users? If so how do you do this? My guess is

Mapper.CreateMap<Group, GroupDto>()     .ForMember(g => g.id, opt => opt.Ignore());     .ForMember(g => g.name, opt => opt.Ignore());     .ForMember(g => g.Users, opt => opt.MapFrom(u => Mapper.Map<Group, UserDto>(u))) 

Is this correct?

Answer 1

1- Change the GroupDto to be like this:

[DataContract] public class GroupDto {     [DataMember]     public int id { get; set; }     [DataMember]     public string name{ get; set; }     [DataMember]     public List<UserDTO> Users { get; set; }       } 

2- Create your mappings :

Mapper.CreateMap<User, UserDto>(); Mapper.CreateMap<UserDto, User>(); // Only if you convert back from dto to entity  Mapper.CreateMap<Group, GroupDto>(); Mapper.CreateMap<GroupDto, Group>(); // Only if you convert back from dto to entity 

3- that's all, because auto mapper will automatically map the List<User> to List<UserDto> (since they have same name, and there is already a mapping from user to UserDto)

4- When you want to map you call :

Mapper.Map<GroupDto>(groupEntity); 

Hope that helps.