dependency-injection .NET - Pure DI examples MVC

Example

public interface ISingleton : IDisposable { }
public class TransientDependency { }

public class Singleton : ISingleton
{
    public void Dispose() { } 
}

public class CompositionRoot : IDisposable, IControllerFactory
{
    private readonly ISingleton _singleton;

    // pass in any true singletons i.e. cross application instance singletons
    public CompositionRoot()
    {
        // intitialise any application instance singletons
        _singleton = new Singleton();
    }

    public void Dispose()
    {
        _singleton.Dispose();
    }

    public IController CreateController(RequestContext requestContext, string controllerName)
    {
        if (controllerName.ToLower() == "home")
        {
            return new HomeController(_singleton, new TransientDependency());
        }

        var argumentException = new ArgumentException(@"Unexpected controller! " + controllerName);
        Log.Error("don't know how to instantiate MVC controller: {controllerType}. redirecting to help", controllerName);
        throw argumentException; // Alternatively would return some default Page Not Found placeholder controller;
    }

    public SessionStateBehavior GetControllerSessionBehavior(RequestContext requestContext, string controllerName)
    {
        return SessionStateBehavior.Default; 
    }

    public void ReleaseController(IController controller)
    {
        // anything to clean up?
    }
}

public static class DependencyInjection
{
    public static void WireUp()
    {
        var compositionRoot = new CompositionRoot();
        System.Web.Mvc.ControllerBuilder.Current.SetControllerFactory(compositionRoot);
    }
}