asp.net mvc 根据路由生成正确的url

假设存在这样一段路由配置：

routes.MapRoute(
name: "ProductList1_01",
url: "pl/{bigSortId}_{smallSortId}_{brandId}.html",
defaults: new { controller = "NewStore", action = "ProductList" },
namespaces: mallNS
);
routes.MapRoute(
name: "ProductList1_02",
url: "pl/{bigSortId}_{smallSortId}.html",
defaults: new { controller = "NewStore", action = "ProductList" },
namespaces: mallNS
);
routes.MapRoute(
name: "ProductList1_03",
url: "pl/{bigSortId}.html",
defaults: new { controller = "NewStore", action = "ProductList" },
namespaces: mallNS
);

如果我希望自动匹配到 pl/{bigSortId}_{smallSortId}.html，我会这样写：

@Url.Action("ProductList", new { bigSortId = Model.BigSortId, smallSortId = Model.SmallSortId, brandId = "" })

但如果页面存在form，并且存在向当前页面的post brandId表单元素，可能造成生成这样的Url：

/pl/11_02.html?brandId=293，导致虽然路由匹配正确，但仍然出现了问号及后面的参数（而这里我是希望生成的链接为：/pl/11_02.html）

为了达到这个目的，而又不将Url写死，修改路由配置为：

routes.MapRoute(
name: "ProductList1_01",
url: "pl/{bigSortId}_{smallSortId}_{brandId}.html",
defaults: new { controller = "NewStore", action = "ProductList" },
namespaces: mallNS
);
routes.MapRoute(
name: "ProductList1_02",
url: "pl/{bigSortId}_{smallSortId}.html",
defaults: new { controller = "NewStore", action = "ProductList" ,brandId="" },
namespaces: mallNS
);
routes.MapRoute(
name: "ProductList1_03",
url: "pl/{bigSortId}.html",
defaults: new { controller = "NewStore", action = "ProductList", smallSortId = "", brandId="" },
namespaces: mallNS
);

解决此问题。