I just shipped a new version of Heroic.AutoMapper. 

Unfortunately, AutoMapper 4.2.0 introduces some breaking changes between 4.1.0 (semvar, anyone?), and Heroic.AutoMapper was impacted.  That means anything that uses Heroic.AutoMapper is also impacted.

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Fortunately, the change is mechanical, and a NuGet package update followed by some find-and-replace should have you back up and running.

First, update to Heroic.AutoMapper 2.0.0. 

Next, do a find-and-replace, replacing “CreateMappings(IConfiguration” with “CreateMappings(IMapperConfiguration”.   Any type that implements IHaveCustomMappings should have changed from this:

public void CreateMappings(IConfiguration configuration)
{
    configuration.CreateMap<Foo, FooViewModel>()
        .ForMember(x => x.Name, opt => opt.MapFrom(x => x.FullName));
}

To this:

public void CreateMappings(IMapperConfiguration configuration)
{
    configuration.CreateMap<Foo, FooViewModel>()
        .ForMember(x => x.Name, opt => opt.MapFrom(x => x.FullName));
}

Going forward, AutoMapper 5.0 is going to be a big change.  I’m still not sure how I feel about it.  On the one hand, I totally agree that having a non-static version of Mapper could be useful, and it will probably clean up a lot of things internally.  But, in every application I’ve ever created, I’ve only ever needed a single Mapper.  I can’t think of a single time I’ve needed a second one.  So, this change is going to add quite a bit of noise to my apps with no real benefit to me.  I’ll have to inject my IMapper now, plus I’ll have to pass the configuration around each time I want to use ProjectTo<T> (which is all the time).  Not good.

Because of that, I do plan to ship a new version of Heroic.AutoMapper that provides a static Mapper when AutoMapper 5.0 is released.  I don’t know exactly what it’ll look like yet, but it may very well expose the same API as the old static Mapper (just backed by a static instance of IMapper now).  The goal is to minimize changes to my existing apps while also keeping things clean and simple.