Automapper: How to not repeat mapping config from complex type to base class

Question

I have a bunch of DTO classes that inherit from this CardBase:

// base class
public class CardBase
{
  public int TransId {get; set; }
  public string UserId  { get; set; }
  public int Shift { get; set; }
}

// one of the concrete classes
public class SetNewCardSettings : CardBase
{
  // specific properties ...
}

In my MVC project I have a bunch of view models with a AuditVm complex type that has the same properties of CardBase:

public class AuditVm
{
  public int TransId {get; set; }
  public string UserId  { get; set; }
  public int Shift { get; set; }
}

public class CreateCardVm : CardVm
{
  // specific properties here ...

  public AuditVm Audit { get; set }
}

Those view models cannot inherit from AuditVm because each of them already has a parent. I thought I could setup my mapping like below so I would not have to specify the map from AuditVm to the CardBase for every view model that has AuditVm as a complex type. But it is not working. How do I properly map from a complex type to a flatten type with properties on the base class?

  Mapper.CreateMap<AuditorVm, CardBase>()
    .Include<AuditorVm, SetNewCardSettings>();

  // this does not work because it ignores my properties that I map in the second mapping
  // if I delete the ignore it says my config is not valid
  Mapper.CreateMap<AuditorVm, SetNewCardSettings>()
    .ForMember(dest => dest.Temp, opt => opt.Ignore())
    .ForMember(dest => dest.Time, opt => opt.Ignore());

  Mapper.CreateMap<CreateCardVm, SetNewCardSettings>()
     // this gives me an error
    .ForMember(dest => dest, opt => opt.MapFrom(src => Mapper.Map<AuditorVm, SetNewCardSettings>(src.Auditor)));

    // I also tried this and it works, but it does not map my specific properties on SetNewCardSettings
    //.ConvertUsing(dest => Mapper.Map<AuditorVm, SetNewCardSettings>(dest.Auditor));

UPDATE: here is the fiddle https://dotnetfiddle.net/iccpE0

CAn you supply an example of a type that you would map to from CreateCardVm such that you would have to map Audit to a property of type CardBase. — Ben Robinson
ooh sorry my last mapping had wrong classes when I copied it over. The last mapping is from CreateCardVm (has AuditVm) to SetNewCardSettings (has CardBase) — jmzagorski
How does the last line (the one using ConvertUsing) work if CreateCardVM doesn't inherit from AuditorVM? — Andrew Whitaker
it works in the sense that it only maps the complex type AuditorVm on CreateCardVm to the base type properties on SetNewCardSettings — jmzagorski
Is there any way you can set up an example that shows the issue on a site like dotnetfiddle.net? — Andrew Whitaker

Andrew Whitaker Andrew Whitaker · Accepted Answer · 2014-12-05T14:36:33

.Include is for a very specific case--you have two identically-structured class hierarchies you'd like to map, for example:

public class AEntity : Entity { }

public class BEntity : Entity { }

public class AViewModel : ViewModel { }

public class BViewModel : ViewModel { }

Mapper.CreateMap<Entity, ViewModel>()
    .Include<AEntity, AViewModel>()
    .Include<BEntity, BViewModel>();

// Then map AEntity and BEntity as well.

So unless you have this kind of situation, .Include isn't the right thing to use.

I think your best bet is to use ConstructUsing:

 Mapper.CreateMap<AuditVm, CardBase>();

 Mapper.CreateMap<AuditVm, SetNewCardSettings>()
     .ConstructUsing(src => 
          {
              SetNewCardSettings settings = new SetNewCardSettings();
              Mapper.Map<AuditVm, CardBase>(src, settings);
              return settings;
          })
     .IgnoreUnmappedProperties();

 Mapper.CreateMap<CreateCardVm, SetNewCardSettings>()
     .ConstructUsing(src => Mapper.Map<SetNewCardSettings>(src.Audit))
     .IgnoreUnmappedProperties();

I've also incorporated this answer's extension method to ignore all unmapped properties. Since we're using ConstructUsing, AutoMapper doesn't know that we've already taken care of those properties.

Updated fiddle: https://dotnetfiddle.net/6ZfZ3z

Automapper: How to not repeat mapping config from complex type to base class

1 Answers