Automapper map from one object to nested objects

Question

What is the best way to map inner objects with Automapper 2.0

1. Use the solution in this question (Automapper 1.0)

2. Create a Custom Value Resolvers

3. ?

   public class DTOObject
   {
       // MainObject
       public int Id { get; set; }
       public string Name { get; set; }
   
       // SubObject (TopObject)
       public string TopText { get; set; }
       public string TopFont { get; set; }
   
       // SubObject (BottomObject)
       public string BottomText { get; set; }
       public string BottomFont { get; set; }
   }
   
   public class MainObject
   {
       public int Id { get; set; }
       public string Name { get; set; }
   
       public SubObject TopObject { get; set; }
       public SubObject BottomObject { get; set; }
   }
   
   public class SubObject
   {
       public string SubPropText { get; set; }
       public string SubPropFont { get; set; }
   }
   

Custom Value Resolvers

    public class CustomResolver : ValueResolver<DTOObject, SubObject>
    {
        protected override SubObject ResolveCore(DTOObject source)
        {
            return Mapper.Map<DTOObject, SubObject>(source);
        }
    }

Lotte

Do you have control of the design of the DTOObject? – Chintz

Yes, and no this is a old data base that is in heavy use. – Culver

Which direction are you trying to go, DTOObject to MainObject or MainObject to DTOObject? – Chintz

Probably best to use Mapper.CreateMap<DTOObject, MainObject>().ForMember(d => d.TopObject, mc => mc.MapFrom(s => new SubObject(){ SubPropText = s.TopText, SubPropFont = s.TopFont } )); – Chintz

Also note, in your CustomResolver you shouldn't call Mapper.Map() you should create the SubObject using the properties from the source and return that. – Chintz

why not call a sub mapping that takes in the same source object and returns the SubObject I need? – Culver

let us continue this discussion in chat – Culver

Answer 1

For me it was possible to use just MapFrom (without ResolveUsing what gives you a chance to use this mapping with IQueryable extensions). So you will get the following in the Automapper configuration:

Mapper.CreateMap<DTOObject, SubObject>()
    .ForMember(dest => dest.SubPropText, opt => opt.MapFrom(x => x.BottomText))
    .ForMember(dest => dest.SubPropFont, opt => opt.MapFrom(x => x.BottomFont));

Mapper.CreateMap<DTOObject, MainObject>()
    .ForMember(dest => dest.TopPart, opt => opt.MapFrom(x => x))
    .ForMember(dest => dest.BottomPart, opt => opt.MapFrom(x => x));

Spadework

Answer 2

I ended up creating my own value resolvers for any SubObjects of MainObject that come from DTOObject.

public class PartResolver<T> : ValueResolver<DTOObject, T>
{
    protected override T ResolveCore(DTOObject source)
    {
        return Mapper.Map<T>(source);
    }
}

Then in my Automapper config I create a map from the DTOObject to SubObject and use the ValueResolver to map that object into the MainObject

Mapper.CreateMap<DTOObject, SubObject>();

Mapper.CreateMap<DTOObject, MainObject>()
    .ForMember(dest => dest.TopPart, opt => opt.ResolveUsing<PartResolver<SubObject>>())
    .ForMember(dest => dest.BottomPart, opt => opt.ResolveUsing<PartResolver<SubObject>>());

Lotte

Answer 3

ResolveUsing is not available with latest version of AutoMapper. So only option left is to use MapFrom. (use @ZedRoth solution).

Disfrock