AutoMapper bidirectional mapping

Question

If I want to do bi-directional mapping, do I need to create two mapping?

Mapper.CreateMap<A, B>() and Mapper.CreateMap<B, A>()?

Stringent

Answer 1

Yes, because if you change the type of some property (for example DateTime -> string) it is not bidirectional (you will need to instruct Automapper how to convert string -> DateTime).

Hine

Makes sense, but it would be nice it the library TRIED to do the mapping as a convention, and you could explicitly disable it if it wasn't working. For example, I map domain objects to view models and bidirectional mapping would work perfectly for me. – Ebracteate

Answer 2

Yes, but if you find yourself doing this often:

public static class AutoMapperExtensions
{
    public static void Bidirectional<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
    {
        Mapper.CreateMap<TDestination, TSource>();
    }
}

then:

Mapper.CreateMap<A, B>().Bidirectional();

Dorladorlisa

while this may not answer the question, it certainly solves the underlying problem posed – Anastomosis

Deprecated in 4.2, Removed in 5 :( #38194512 – Photomural

Answer 3

This is now baked into AutoMapper

Mapper.CreateMap<SourceType, DestType>().ReverseMap();

Lezlie

This does not work with custom mappings, only when the property names are the same in both classes. – Gerri

@MichaelBrown even then, ReverseMap called on IMappingExpression<SourceType, DestType> returns an IMappingExpression<DestType, SourceType>, so the reverse custom mapping can then be defined. I move this be the new accepted answer. – Syncarpous

Answer 4

Great idea Eric! I've added a return value, so the reverse mapping is configurable too.

public static class AutoMapperExtensions
{
    public static IMappingExpression<TDestination, TSource> Bidirectional<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
    {
        return Mapper.CreateMap<TDestination, TSource>();
    }
}

Abyss