Generate wrong outgoing url because of segment variable reuse in MVC 4 - asp.net-mvc-4

Question

Here is my RouteConfig.cs
routes.MapRoute(null,
"{controller}/Page{page}",
new {controller = "Product", action = "Index", category = (string) null},
new {page = #"\d+"}
);
routes.MapRoute(null,
"{controller}/{category}",
new {controller = "Product", action = "Index", page = 1}
);
routes.MapRoute(null,
"{controller}/{category}/Page{page}",
new {controller = "Product", action = "Index"},
new {page = #"\d+"}
);
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);
And here is the code for generating url:
#Html.ActionLink("View Cart", "Index", "ShoppingCart", null, new { #class = "btn btn-orange" })
It works well when I navigate to, for example, Product/Page2, Product/Laptop, Product/Laptop/Page2. The problem is, whenever my current URL contains Page segment, it will try to reuse that segment for generating outgoing URL. So, if I'm at Product/Page2 the above generated URL would be ShoppingCart/Page2. I don't know how to avoid this.
Please help me. Thank you so much.
EDIT!!!
I've found a workaround way. Instead of using ActionLink, I use RouteLink like this:
#Html.RouteLink("View Cart", "Default", new { controller = "ShoppingCart", action = "Index" }, new { #class = "btn btn-orange" })
But I still want to use ActionLink, so please help me.
EDIT!!!
The workaround way doesn't work when I generate a link to ShoppingCart/Checkout. It still take me to Index action in ShoppingCart controller.

Answer 1

Create a new route pattern specific to ShoppingCart and make it the first route by placing it at the TOP.
routes.MapRoute(null,
"ShoppingCart/{action}",
new {controller = "Product"});
);
As a rule all the specific routes should come first.

Answer 2

This is because of the way the routing system tries to evaluate the value of segment variables when trying to match against a route.
So when the call to render the link occurs with the following arguments:
#Html.ActionLink("View Cart", "Index", "ShoppingCart", null, new { #class = "btn btn-orange" })
the framework when evaluating the route with template
{controller}/Page{page}
will resolve the controller segment variable to be ShoppingCart however when it cannot find a value for the page segment variable (via any of the arguments in the method call), it will then try and resolve that value from the RouteData object in the ViewContext. Since you have navigated to Product/Page2, the current value of page within the routes value dictionary is 2.
You can inspect this by looking at the value of ViewContext.RouteData.Values["page"] when rendering that view.