AutoMapper DynamicMap with DataReader against an interface

Question

I am relatively new to AutoMapper but found it very powerful in transforming my objects within a WCF service into DTOs (kind of the point).

Today I ran into a situation that I thought should work but fails. I am programming against interfaces in most places and a lot of my maps (that work) actually map EF entities to my DTO's interfaces (i.e. Mapper.CreateMap();).

However I ran into a situation where I have a datatable and I wanted to use AutoMapper to convert it. I quickly found some samples that looked promising but they kept failing with relatively vague exception (at least to me).

As a test, I changed the DynamicMap call to use the concrete implementation of the DTO and it worked successfully. I initially didn't go this route because all of the maps I created previously against interfaces which are resolved by my IoC container (Unity 3.x) worked.

Is there a way to get this particular map to work using the interface or do I have to use the concrete class when doing dynamic maps that return collections?

Failing:

AutoMapper.Mapper.DynamicMap<IDataReader, IEnumerable<IPunctuationMapDto>>(table.CreateDataReader());

Working:

AutoMapper.Mapper.DynamicMap<IDataReader, IEnumerable<PunctuationMapDto>>(table.CreateDataReader());

PunctuationMapperDto:

[DataContract]
public class PunctuationMapDto : IPunctuationMapDto
{
    [DataMember]
    public int Id { get; set; }

    [DataMember]
    public string TaggedValue { get; set; }

    [DataMember]
    public int UntaggedValue { get; set; }
}

IPunctuationMapDto:

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


    string TaggedValue { get; set; }


    int UntaggedValue { get; set; }
}

Answer 1

Jimmy Bogard, AutoMapper creator replied in a different forum:

The data reader mapper doesn't support interfaces, only concrete classes. This is because the data reader mapper is implemented using reflection.emit for speed.