Map complex type to flat type in AutoMapper

Question

I have a complex object like:

public class BusinessUnit
{
        public TradingDesk TradingDesk { get; }
        public string Division { get; }

        public BusinessUnit(string division, TradingDesk tradingDesk)
        {
            Division = division;
            TradingDesk = tradingDesk;
        }
}

I want to map this to the flat type:

public class Row
{
   //TradingDesk properties
   public string TraderFirstName { get; set; }
   public string TraderLastName { get; set; }
   public string TradingDeskName { get; set; }

   public string Division { get; set; }
}

I have already configured AutoMapper for TradingDesk:

CreateMap<TradingDesk, Row>().ForMember(vm => vm.TradingDeskName, op => op.MapFrom(src => src.Name));

so the following test is passing:

[Test]
public void Should_Map_TradingDesk_To_Row()
{
    var tradingDesk = Fixture.Create<TradingDesk>();

    var mapped = AutoMapper.Map<Row>(tradingDesk);

    mapped.TradingDeskName.Should()
            .Be(tradingDesk.Name);
    mapped.TraderFirstName.Should()
            .Be(tradingDesk.Trader.FirstName);
    mapped.TraderLastName.Should()
            .Be(tradingDesk.Trader.LastName);
}

But when I try to map BusinessUnit to Row I am having to reconfigure AutoMapper for TradingDesk as such:

CreateMap<BusinessUnit, Row>()
   .ForMember(vm => vm.TradingDeskName, op => op.MapFrom(src => src.TradingDesk.Name))
   .ForMember(vm => vm.TraderFirstName, op => op.MapFrom(src => src.TradingDesk.Trader.FirstName))
   .ForMember(vm => vm.TraderLastName, op => op.MapFrom(src => src.TradingDesk.Trader.LastName));

I expect that AutoMapper should use the already configured source & destination type mapping when it needs to map TradingDesk to Row while mapping BusinessUnit. This way I can build the configuration from the smallest to the largest type while flattening out a complex object without having to define mapping for each individual member in the flattened type.

Answer 1

Actual syntax might differ because I'm using AutoMapper in a static manner, but the principle remains the same:

Mapper.CreateMap<BusinessUnit, Row>()
      .ConvertUsing(source => Mapper.Map<TradingDesk, Row>(source.TradingDesk));