Mapping one source class to multiple derived classes with automapper

Question

Suppose i have a source class:

public class Source
{
    //Several properties that can be mapped to DerivedBase and its subclasses
}

And some destination classes:

public class DestinationBase
{
     //Several properties
}

public class DestinationDerived1 : DestinationBase
{
     //Several properties
}

public class DestinationDerived2 : DestinationBase
{
     //Several properties
}

Then I wish the derived destination classes to inherit the automapper configuration of the baseclass because I do not want to have to repeat it, is there any way to achieve this?

Mapper.CreateMap<Source, DestinationBase>()
    .ForMember(...)
    // Many more specific configurations that should not have to be repeated for the derived classes
    .ForMember(...);

Mapper.CreateMap<Source, DestinationDerived1 >()
    .ForMember(...);
Mapper.CreateMap<Source, DestinationDerived2 >()
    .ForMember(...);

When I write it like this it does not use the base mappings at all, and include doesn't seem to help me.

Edit: This is what I get:

public class Source
{
    public string Test { get; set; }
    public string Test2 { get; set; }
}

public class DestinationBase
{
    public string Test3 { get; set; }
}

public class DestinationDerived1 : DestinationBase
{
    public string Test4 { get; set; }
}

public class DestinationDerived2 : DestinationBase
{
    public string Test5 { get; set; }
}

---

Mapper.CreateMap<Source, DestinationBase>()
              .ForMember(d => d.Test3, e => e.MapFrom(s => s.Test))
              .Include<Source, DestinationDerived1>()
              .Include<Source, DestinationDerived2>();

        Mapper.CreateMap<Source, DestinationDerived1>()
              .ForMember(d => d.Test4, e => e.MapFrom(s => s.Test2));

        Mapper.CreateMap<Source, DestinationDerived2>()
              .ForMember(d => d.Test5, e => e.MapFrom(s => s.Test2));

AutoMapper.AutoMapperConfigurationException : Unmapped members were found. Review the types and members below.

Add a custom mapping expression, ignore, add a custom resolver, or modify the source/destination type

Source -> DestinationDerived1 (Destination member list)

Test3

Answer 1

Include derived mappings into base mapping:

Mapper.CreateMap<Source, DestinationBase>()
    .ForMember(d => d.Id, op => op.MapFrom(s => s.Id)) // you can remove this
    .Include<Source, DestinationDerived1>()
    .Include<Source, DestinationDerived2>();

Mapper.CreateMap<Source, DestinationDerived1>()
    .ForMember(d => d.Name, op => op.MapFrom(s => s.Text))
    .ForMember(d => d.Value2, op => op.MapFrom(s => s.Amount));

Mapper.CreateMap<Source, DestinationDerived2>()
    .ForMember(d => d.Value, op => op.MapFrom(s => s.Amount));

Usage:

Mapper.AssertConfigurationIsValid();
var s = new Source() { Id = 2, Amount = 10M, Text = "foo" };
var d1 = Mapper.Map<DestinationDerived1>(s);
var d2 = Mapper.Map<DestinationDerived2>(s);

See Mapping inheritance on AutoMapper wiki.

---

UPDATE: Here is full code of classes which works as it should.

public class Source
{
    public int Id { get; set; }
    public string Text { get; set; }
    public decimal Amount { get; set; }
}

public class DestinationBase
{
    public int Id { get; set; }
}

public class DestinationDerived1 : DestinationBase
{
    public string Name { get; set; }
    public decimal Value2 { get; set; }
}

public class DestinationDerived2 : DestinationBase
{
    public decimal Value { get; set; }
}

---

UPDATE (workaround of AutoMapper bug):

public static class Extensions
{
    public static IMappingExpression<Source, TDestination> MapBase<TDestination>(
        this IMappingExpression<Source, TDestination> mapping)
        where TDestination: DestinationBase
    {
        // all base class mappings goes here
        return mapping.ForMember(d => d.Test3, e => e.MapFrom(s => s.Test));
    }
}

And all mappings:

    Mapper.CreateMap<Source, DestinationBase>()
          .Include<Source, DestinationDerived1>()
          .Include<Source, DestinationDerived2>()
          .MapBase();

    Mapper.CreateMap<Source, DestinationDerived1>()
          .MapBase()
          .ForMember(d => d.Test4, e => e.MapFrom(s => s.Test2));

    Mapper.CreateMap<Source, DestinationDerived2>()
          .MapBase()
          .ForMember(d => d.Test5, e => e.MapFrom(s => s.Test2));

Answer 2

For Automapper 8.0.
Current version has new method IncludeAllDerived
Here's working example:

        var config = new MapperConfiguration(cfg =>
        {
            cfg.CreateMap<Source, DestinationBase>()
                .ForMember(dest => dest.Test3, opt => opt.MapFrom(src => src.Test))
                .IncludeAllDerived();

            cfg.CreateMap<Source, DestinationDerived1>()
                .ForMember(dest => dest.Test4, opt => opt.MapFrom(src => src.Test2));

            cfg.CreateMap<Source, DestinationDerived2>()
                  .ForMember(dest => dest.Test5, opt => opt.MapFrom(src => src.Test2));
        });

        var mapper = config.CreateMapper();

        var source = new Source { Test = "SourceTestProperty", Test2 = "SourceTest2Property" };
        var d1 = mapper.Map<DestinationDerived1>(source);
        var d2 = mapper.Map<DestinationDerived2>(source);

        Assert.Equal("SourceTestProperty", d1.Test3);
        Assert.Equal("SourceTest2Property", d1.Test4);

        Assert.Equal("SourceTestProperty", d2.Test3);
        Assert.Equal("SourceTest2Property", d2.Test5);

Answer 3

NB! For those who are having issues with derived interfaces. AutoMapper does not support registering against derived interfaces. Only classes are handled.

To make it work, you have to change your type reference for CreateMap to the class instead of interface.

Example:

interface Interface1 {}
class Class1: Interface1 {}
interface Interface2: Interface1 {}
class Class2: Class1, Interface2 {}

CreateMap<OtherClass, Interface1>().IncludeAllDerived();
CreateMap<OtherClass, Interface2>();

Any mapping against Interface2 will only use the first CreateMap. You will have to identify the second as

CreateMap<OtherClass, Class2>();