DTO的地图组件也属于DTO

Question

This is my class which holds database data:

public partial class PermissionGroup
{
    public int Id { get; set; }
    public string Name { get; set; }
    // other database properties

    public virtual ICollection<GroupActionPermission> GroupActionPermissions { get; set; }
}

And that's my dto's:

public class PermissionGroupDTO
{
    public int Id { get; set; }
    public string Name { get; set; }

    public ICollection<GroupActionPermissionDTO> ActionPermissions { get; set; }
}

public class GroupActionPermissionDTO
{
    public int Id { get; set; }
    public int GroupId { get; set; }
    public int PermissionActionId { get; set; }

    public PermissionGroupDTO Group { get; set; }
}

Now, I am making mapping:

public IEnumerable<PermissionGroupDTO> GetGroups()
{
    return OnConnect<IEnumerable<PermissionGroupDTO>>(db =>
    {
        return db.PermissionGroups
        .Include(i => i.GroupActionPermissions)
        .ProjectTo<PermissionGroupDTO>()
        .ToList();
    });
}

And I am getting collection of PermissionGroupDTO which should contains collection of GroupActionPermissionDTO , but that collection stays null . Is there something wrong with my code? I am afraid that automapper can map collections from foreign keys.

Also, thats my automapper initializer:

Mapper.Initialize(cfg =>
{
    cfg.CreateMap<PermissionGroup, PermissionGroupDTO>();
    cfg.CreateMap<GroupActionPermission, GroupActionPermissionDTO>();
});

Answer 1

I believe the reason is desribed here http://docs.automapper.org/en/stable/Queryable-Extensions.html

Note that for this feature to work, all type conversions must be explicitly handled in your Mapping.

So that means you should manually configure the mapping:

Mapper.Initialize(cfg =>
{
    cfg.CreateMap<PermissionGroup, PermissionGroupDTO>()
       .ForMember(dto => dto.ActionPermissions , conf => conf.MapFrom(ol => ol.GroupActionPermissions )));;
    cfg.CreateMap<GroupActionPermission, GroupActionPermissionDTO>();
});

BTW, note that fields are named differently: GroupActionPermissions vs. ActionPermissions . This is also the reason why automapper doesn't map it automatically and then you should use the manual configuration I wrote.