public class NinjectControllerFactory : DefaultControllerFactory
    {
        private IKernel ninjectKernel;

        public NinjectControllerFactory()
        {
            ninjectKernel = new StandardKernel();
            AddBindings();
        }

        protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
        {
            return controllerType == null
                ? null
                : (IController)ninjectKernel.Get(controllerType);
        }

        private void AddBindings()
        {
            ninjectKernel.Bind<ICategoryRepository>().To<SQLCategoryRepository>();
        } 

    }

ControllerBuilder.Current.SetControllerFactory(new NinjectControllerFactory());

public ActionResult CategoryMenu(ICategoryRepository categoryRepository)
        {
            category = categoryRepository;
            var cat = categoryRepository.getCategory();
            return PartialView(cat);
        }