ASP.NET MVC Framework and Unity Dependency Injection Container Part II

I received a few emails on showing more detail on how I am using the ASP.NET MVC Framework with the Unity Dependency Injection Container. I am still deciding the best way to integrate the various IoC Containers with the ASP.NET MVC Framework, but this time I used the same approach as the Windsor Example in MVCContrib.

The HttpApplication Class is responsible for holding the Unity Container and providing access to it using an IContainerAccessor Interface:

public class Global : HttpApplication, IContainerAccessor
{
    private static UnityContainer _container;

    public static IUnityContainer Container
    {
        get { return _container; }
    }

    IUnityContainer IContainerAccessor.Container
    {
        get { return Container; }
    }

    protected void Application_Start(object sender, EventArgs e)
    {
        InitializeContainer();
        ControllerBuilder.Current.
            SetDefaultControllerFactory(
                    typeof(CustomControllerFactory));
    }

    private void InitializeContainer()
    {
        if (_container == null)
            _container = new UnityContainer();
            
        // For Sample Only...
        _container.RegisterType<INewsService, NewsService>();
    }
}

As mentioned in the previous post, Unity Dependency Injection Container and ASP.NET MVC Framework, I am not adding any Controller Classes to the Unity Container. You don't need to with Unity. It will create classes even if they are not in the container.

I am specifying my custom IControllerFactory, CustomControllerFactory, and I am registering the NewsService that will be injected into my HomeController.

As mentioned in the previous post, my CustomControllerFactory is as follows:

public class CustomControllerFactory : IControllerFactory
{
    public IController CreateController
            (RequestContext context, Type controllerType)
    {
        IContainerAccessor containerAccessor =
            context.HttpContext.ApplicationInstance
                 as IContainerAccessor;

        return containerAccessor.Container.Resolve(controllerType)
            as IController;
    }
}

It may look a little confusing looking at it like this, because I am accessing the UnityContainer through a IContainerAccessor Interface and the Container Property on that interface. All I am doing is using the following method on the UnityContainer API:

UnityContainer.Resolve(Type t)

that will create the HomeController Class and add any dependencies to it.

Using the Property Setter Injection Mechanism mentioned in the previous post, since the HomeController has a [Dependency] Attribute on the NewsService Property:

public class HomeController : Controller
{
    [Dependency]
    public INewsService NewsService { get; set; }

    [ControllerAction]
    public void Index()
    {
        List<News> currentNews = NewsService.GetNews();
        RenderView("Index", currentNews);
    }
}

Unity will inject the NewsService we registered before into the HomeController. As mentioned above, we registered the NewsService in the InitializeContainer Method just for this sample -

private void InitializeContainer()
{
    if (_container == null)
        _container = new UnityContainer();
        
    // For Sample Only...
    _container.RegisterType<INewsService, NewsService>();
}

Note that if you wanted to register the NewsService as a Singleton, you could register it as follows:

_container
    .RegisterType<INewsService, NewsService>
       (new ContainerControlledLifetimeManager());

I hope that clarifies how I used Unity with the ASP.NET MVC Framework. This is just one way that I modeled after the Windsor Example in the MVCContrib.

Recent ASP.NET MVC Tutorials:

Author: David Hayden, Microsoft MVP C#

Site: http://www.davidhayden.com/

posted on Thursday, February 14, 2008 10:34 AM