AutoMapper & AutoFac


So I tend to develop things in the way of

  1. Make it work
  2. Make it pretty

Make it work

So when using AutoMapper after step one I ended up with something like this

.ForMember(d => d.SomeSource, 
     o => o.MapFrom(
          s => new Serializer().Deserialize<SomeViewModel>(s.Serialized)))

Some background, for the destination SomeSource I needed to Deserialize the value as it was currently stored as Json in my database.

Make it pretty

While it works it looks rather horrible, so I started looking into something that allowed me to get a ISerializer from AutoFac (my IoC of choice) instead.

So, first I added a custom ValueResolver that looked like this

public class SomeViewModelResolver 
    : ValueResolver<OrderRow, ScheduleViewModel>
        private readonly ISerializer _serializer;

        public ScheduleViewModelResolver(ISerializer serializer)
            _serializer = serializer;

        protected override SomeViewModel ResolveCore(Source source)
            return _serializer.Deserialize<SomeViewModel>(source.Serialized);

Next was to connect AutoMapper with AutoFac and to register the ValueResolver:

// Register my new valueresolver

// Connect AutoMapper to AutoFac
Mapper.Initialize(x => x.ConstructServicesUsing(container.Resolve));

Once that is done the last thing to change is to modify the ForMember call to use the new ValueResolver instead

.ForMember(d => d.SomeSource, o => o.ResolveUsing<SomeViewModelResolver>())

Looks a lot cleaner and follows the flow that you would expect when using a IoC container.


If you don’t want to have calls to the static Mapper.Map<> all over your code, it is possible to register the IMappingEngine in AutoMapper in you IoC container and have that as an dependency for you class too. For AutoFac the registration looks like this

builder.Register(c => Mapper.Engine).As<IMappingEngine>().SingleInstance();

The important thing is to register it as a singelton. Once that is done just add IMappingEngine mappingEngine to the constructors of those classes that use AutomMapper.