Using Unity to inject dependencies into a custom ActionFilter

At the moment, I have a custom ControllerFactory into which I inject my Unity container:

in global.asax Application_Start():

var container = InitContainer();
DependencyResolver.SetResolver(new UnityDependencyResolver(container));

var factory = new UnityControllerFactory(container);
ControllerBuilder.Current.SetControllerFactory(factory);

In the controller factory I set my controllers to use a custom ActionInvoker like so:

protected override IController GetControllerInstance(System.Web.Routing.RequestContext requestContext, Type controllerType)
{
    var controller = base.GetControllerInstance(requestContext, controllerType) as Controller;

    if (controller != null)
        controller.ActionInvoker = new UnityActionInvoker(_container);

    return controller;
}

Finally in my custom ActionInvoker, I attempt to buildup actions being invoked using the ActionInvokers container:

protected override ActionExecutedContext InvokeActionMethodWithFilters(
        ControllerContext controllerContext,
        IList<IActionFilter> filters,
        ActionDescriptor actionDescriptor,
        IDictionary<string, object> parameters)
{
    var builtUpFilters = new List<IActionFilter>();

    foreach (IActionFilter actionFilter in filters)
    {
        builtUpFilters.Add(_container.BuildUp<IActionFilter>(actionFilter));
    }

    return base.InvokeActionMethodWithFilters(controllerContext, builtUpFilters, actionDescriptor, parameters);
}

Here is an example of one of the ActionFilters that is being built up:

public class PopulatRolesAttribute : ActionFilterAttribute, IActionFilter
{
    private const string RolesKey = "roles";

    [Dependency]
    public Func<IMetadataService> Service { get; set; }

    public PopulatRolesAttribute()
    {
    }

    public override void OnActionExecuting(ActionExecutingContext filterContext)