Question

I’m trying to autowire up my application using Autofac. All is fine apart from the fact I have an abstract generic type such as:

public abstract class Transformer<TModel>
{
  // Some abstract methods
}

With it implemented as:

public class EventTransformer : Transformer<Event>
{
  // implementation of methods
}

I’m autowiring up the application with:

builder.RegisterAssemblyTypes(typeof (MyAssemblyName).Assembly)
    .InstancePerLifetimeScope();

Autofac will then throw an error when resolving this type of class:

public class RandomClass<TModel>
{ 
  public RandomClass(Transformer<TModel> transformer() 
  {
     // Constructor code
  }
}

I get the error below (simplified). I can register the EventTransformer manually as Transformer < Event > and everything works fine, but I don’t want to have to register it manually, I should be able to do it automatically so I can simply create a new class and it’s straight into the application.

The requested service Transformer`1[[Event]]' has not been registered. To avoid this exception, either register a component to provide the service, check for service registration using IsRegistered(), or use the ResolveOptional() method to resolve an optional dependency.

I did try and use the method .AsImplementedInterfaces() when registering the classes but it didn’t seem to work.

So what should I be doing to accomplish this? Also for bonus points, I have no way of knowing what Autofac is registering and what it’s registering it as. Is there anyway of doing this?

Answer 1

You need to register the open generic types with the AsClosedTypesOf method during assembly scanning:

builder.RegisterAssemblyTypes(typeof(MyAssemblyName).Assembly)
    .InstancePerLifetimeScope();
builder.RegisterAssemblyTypes(typeof(MyAssemblyName).Assembly)
    .AsClosedTypesOf(typeof(Transformer<>))
    .InstancePerLifetimeScope();

And you can get the registered components with:

IContainer container = builder.Build();
var registrations = container.ComponentRegistry.Registrations;