How to merge two nested object into one using AutoMapper

November 8, 2021

Hi I have been using AutoMapper to convert my objects, and now I’m trying to merge two nested objects into one, but I can’t figure out how to do it.

I have the following code:

These are my source objects

class SourceSubItemA
{
    string subPropertyA;
}

class SourceSubItemB
{
    string subPropertyB;
}

class Source
{
    SourceSubItemA subItemA;
    SourceSubItemB subItemB;
}

Destination objects

class DestinationSubItem
{
    string propertyA;
    string propertyB;
}

class Destination
{
    DestinationSubItem destItem;
}

This is my Automapper configuration

Mapper.CreateMap<SourceSubItemA, DestinationSubItem>()
    .ForMember(dest => propertyA, opt => opt.MapFrom(src => src.subPropertyA));

Mapper.CreateMap<SourceSubItemB, DestinationSubItem>()
    .ForMember(dest => propertyB, opt => opt.MapFrom(src => src.subPropertyB));

// Probably I have to do something more here.
Mapper.CreateMap<Source, Destination>()
    .ForMember(dest => dest.destItem, opt => opt.MapFrom(src => src.subItemA));

And finally I’m using the mapper by this way

Mapper.Map<Destination>(sourceObject);

The expected result must be a Destination object with a subitem with both properties filled.

Please Help!

>Solution :

As I can see, Destination is just a wrapper of DestinationSubItem that is the one that really needs to get the values from Source.

In that case, you could define a mapper from Source to Destination that puts in dest.destItem the result of mapping from Source directly to DestinationSubItem.

Here an example:

    Mapper.CreateMap<Source, Destination>()
      .ForMember(dest => dest.destItem, opt => opt.MapFrom(src => Mapper.Map<DestinationSubItem>(src)); 

    Mapper.CreateMap<Source, DestinationSubItem>()
      .ForMember(dest => dest.propertyA, opt => opt.MapFrom(src => src.subItemA.subPropertyA)
      .ForMember(dest => dest.propertyB, opt => opt.MapFrom(src => src.subItemB.subPropertyB);