Where shall I put the AutoMapper configuration?

Question

I have AutoMapper mappings, which look like this:

Mapper.Initialize(cfg =>
    {
        cfg.CreateMap<Person, PersonViewModel>();
        cfg.CreateMap<Order, OrderViewModel>();
    });

I am trying to figure out where to put this code in an MVC application. There are two options:

1) Composition Root

public class CompositionRoot : IWindsorInstaller
    {
      //Castle Windosr configuration goes here
      //Call to AutoMapper configuration class here
    }

2) Global.asax

Questions like this suggest it: Where to place AutoMapper.CreateMaps?

My gut is telling me to put it in the Composition Root, however everywhere I read tells me to put it in the Global.asax.

Answer 1

If you take a look in Global.asax at Application_Start. You can already see things like RouteConfig.RegisterRoutes etc. These typically call static methods on classes in the App_Start folder. I usually add a class called AutoMapperConfig with a static method called Configure. I then add this to the list in Gloabl.asax. See below:

void Application_Start(object sender, EventArgs e)
{
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
    ModelBindersConfig.Configure();
    DevExpressConfig.Configure();
    AutoMapperConfig.Configure();          
}

Answer 2

In the past I have registered them as part of a static call from Global.asax. However, the static Mapper.Map methods are being deprecated so I've recently created a static class to setup the configuration mappings. I then call this within the composition root of my application to register the IMapper object that I can then take as a dependency in any classes.

E.g.

public static class AutoMapperConfig
{
  public static MapperConfiguration ConfigureMapping()
  {
    return new MapperConfiguration(cfg =>
    {
      cfg.CreateMap<Person, PersonViewModel>();
      cfg.CreateMap<Order, OrderViewModel>();
    });
  }
}

Using Castle Windsor you could do something like:

container.Register(
  Component.For<IMapper>()
    .UsingFactoryMethod(() => AutoMapperConfig.ConfigureMapping().CreateMapper())
    .LifeStyle.Singleton);