[HttpGet("{catId}/{prodId}")]
public async Task<IActionResult> GetProduct(int catId, int prodId)
{
    // ...
}

[HttpGet]
        [Route("")]
        //[Route("Catalog/Index/{categorySelected:int}/{productTypeSelected:int}")] -- this does not work yet
        [Route("Catalog/Index/{brandSelected:int}")] // Brand belongs to nothing, we only want brand for the visual display of brands available in any given category
        public async Task<IActionResult> Index(int? categorySelected, int? productTypeSelected, int? brandSelected, int? page)
        {
            int pageSize = 3; // Page size, temporary. Not sure where to put this.
            int totalProductCount = (await _services.GetAllProducts()).Count();

            IndexViewModel viewModel = new IndexViewModel
            {
                Products = await _services.GetProducts(productTypeSelected, brandSelected, page ?? 1, pageSize),
                ProductType = await _services.GetAllProductTypes(),
                Brand = await _services.GetAllBrands(),
                Category = await _services.GetAllCategories(),
                PaginationHelper = new PaginationHelper()
                {
                    Page = page ?? 1,
                    ProductCount = totalProductCount,
                    PageCount = (int)Math.Ceiling(((decimal)totalProductCount / pageSize)),
                }
            };

            viewModel.PaginationHelper.NextIsEnabled = ((page ?? 1) < viewModel.PaginationHelper.PageCount) ? true : false; 
            viewModel.PaginationHelper.PreviousIsEnabled = (page > 1) ? true : false;

            return View(viewModel);
        }

        [HttpPost]
        public async Task<IActionResult> Index(IndexViewModel vm, int? page)
        {
            // This is where we do validation

            return RedirectToAction("Index",
                new { categorySelected = vm.CategorySelected, 
                    productTypeSelected = vm.ProductTypeSelected, 
                    brandSelected = vm.BrandSelected, 
                    page = page,
                });
        }

[HttpGet]
        [Route("")]
        //[Route("Catalog/Index/{categorySelected:int}/{productTypeSelected:int}")] -- this does not work yet
        [Route("Catalog/Index/{brandSelected:int}")] 

        [HttpGet("Catalog/Index/{brandSelected:int}")] 

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Catalog}/{action=Index}/{id?}");