C#MVC自定义路由设计

默认路由为：

routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{category}",
            defaults: new { controller = "Home", action = "Index", category = UrlParameter.Optional }
        );

正在生成的URL如下所示：www.domain.com/Home/Index/Category

但如果用户正在浏览特定类别，我希望URL看起来像这样：www.domain.com/Home/category

如果没有选择类别：www.domain.com/Home

我添加了这个代码：

routes.MapRoute(null, "{controller}/{category}", new { action = "Index" });
routes.MapRoute(null, "{controller}/{action}", new { controller = "Home", action = "Index", category = (string)null });

URL开始看起来像我想要的那样，但是！在控制器中调用操作的Form方法不再工作：

@using (Html.BeginForm("AddToCart", "Home"))
                            {                
                                @Html.Hidden("category", Model.CurrentCategory)
                                @Html.Hidden("productId", p.ProductId)
                                <input type="submit" value="Add To Cart" />
                            }

由于某种原因，表单操作方法似乎调用了错误的路由即：

routes.MapRoute(null, "{controller}/{category}", new { action = "Index" });

而不是

routes.MapRoute(null, "{controller}/{action}", new { controller = "Home", action = "Index", category = (string)null });

因为当点击提交按钮时，浏览器重定向到网址：www.domain.com/Home/AddToCart，并且"主页"控制器中的操作方法"AddToCart"从未被调用。

     routes.MapRoute(null, "{controller}/{category}", new { action = "Index" });

     routes.MapRoute(null, "{controller}/{category}", new { action = "Index" });

     routes.MapRoute(null, "{controller}/{action}", new { controller = "Home", action = "Index", category = (string)null });