WebApi Controller Dependency Injection using Unity Container

UnityControllerFactory

// I'm not sure if this is the best or most correct way to do it, but it seems to work in my prototype. 
// Basically, I want "dependency injection" for my controller, and after reading some tech blogs online,
// it seems like the best way to do this is to use IHttpControllerActivator to inject dependencies into 
// your controller because you will have context of the request doing it this way as opposed to doing it 
// via traditional dependency injection.

// this code in Global.asax.cs
public WebApiApplication()
{
    this.container = new UnityContainer();

    container.RegisterType<IMyRepository, MyRepository>(new HierarchicalLifetimeManager());
    container.RegisterType<IModelFactory<dbModel, dto>, MyDtoFactory>(new HierarchicalLifetimeManager());
}

protected void Application_Start()
{
    GlobalConfiguration.Configure(WebApiConfig.Register);

    GlobalConfiguration.Configuration.Services.Replace(
        typeof(IHttpControllerActivator),
        new UnityControllerFactory(this.container));
}

// UnityControllerFactory to do injection
public class UnityControllerFactory : IHttpControllerActivator
{
    private readonly IUnityContainer container;

    public UnityControllerFactory(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }

    public IHttpController Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)
    {
        IUnityContainer childContainer = this.container.CreateChildContainer();
        var controller = (IHttpController)childContainer.Resolve(controllerType);

        request.RegisterForDispose(new Release(() => childContainer.Dispose()));

        return controller;
    }
}

internal class Release: IDisposable
{
    private readonly Action release;

    public Release(Action release)
    {
        this.release = release;
    }

    public void Dispose()
    {
        this.release();
    }
}

// my controller
public FundsController(IMyRepository repository, IModelFactory<dbModel, dto> factory)
{
    this.repository = repository;
    this.factory = factory;
}