Use AutoMapper to map from an interface to a concrete type

Question

I've created a dotNetFiddle that demonstrates the question here .

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Here's a simplified example of what I'm trying to do... let's say I have an the following interfaces:

public interface IPerson
{   
    int Id { get; set; }     
}

public interface IModelPerson : IPerson
{
    int BeautyCompetitionsWon { get; set; }
}

In the real implementation, there are lots of different types of people (eg IUglyPerson , etc). These are the contracts for entity types, eg as follows:

public class PersonEntity : IPerson
{
    public int Id { get; set; }
}

public class ModelPersonEntity : PersonEntity, IModelPerson
{
    public int BeautyCompetitionsWon { get; set; }
}

Note : We may also have multiple implementations of each contract type - eg IModelPerson may also be implemented by SupermodelEntity .

We want to map our entity types to DTOs, which look something like this:

public abstract class PersonDto : IPerson
{
    public int Id { get; set; }
    public abstract string PersonType { get; }
}

public class ModelPersonDto : PersonDto, IModelPerson
{
    public int BeautyCompetitionsWon { get; set; }
    public override string PersonType
    {
        get { return "Model"; }
    }
}

As such, we create a mapping:

Mapper.Initialize(config =>
{
    config.CreateMap<IPerson, PersonDto>()
        .Include<IModelPerson, ModelPersonDto>()
        .ConstructUsing((IPerson person) => 
        {
            if (person is IModelPerson) return new ModelPersonDto();

            throw new InvalidOperationException("Unknown person type: " + person.GetType().FullName);
        })
        ;

    config.CreateMap<IModelPerson, ModelPersonDto>();
});

So, I have two issues here.

1. Is there any way of creating the mappings without the ConstructUsing clause? I thought that having the more specific version of CreateMap would have taken care of this for us, but if I don't have the ConstructUsing clause, AutoMapper tells me "Instances of abstract classes cannot be created".

2. Why don't the properties from my subclasses get mapped? If I execute a mapping as follows:

var source = new ModelPersonEntity { Id = 100, BeautyCompetitionsWon = 9 };
var target = Mapper.Map<PersonDto>(source);

The expected value for target.BeautyCompetitionsWon is 9, but the actual value is 0.

Answer 1

Question 1: Not that I am aware of.

Question 2: When using the .ConstructUsing() make sure you return the mapped object you are after rather than a fresh instance.

eg

Mapper.Initialize(config =>
{
    config.CreateMap<IPerson, PersonDto>()
        .Include<IModelPerson, ModelPersonDto>()
        .ConstructUsing((IPerson person) => 
        {
            if (person is IModelPerson) return Mapper.Map<ModelPersonDto>(person);

            throw new InvalidOperationException("Unknown person type: " + person.GetType().FullName);
        })
        ;

    config.CreateMap<IModelPerson, ModelPersonDto>();
});