Why we use routing in asp.net mvc - asp.net-mvc

Question

why use custom routing in asp.net MVC
for example
RouteConfig.cs
public class RouteConfig
{
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
//Enable Routing
routes.MapMvcAttributeRoutes();
//custom route for about page
//routes.MapRoute(
// name:"about",
// url: "Home/About",
// defaults: new { controller = "Home",action= "About", id=UrlParameter.Optional}
// );
//custom route for contactus page
//routes.MapRoute(
// name: "about",
// url: "Home/ContactUs",
// defaults: new { controller = "Home", action = "ContactUs", id = UrlParameter.Optional }
// );
//default route
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);
}
}
HomeController.cs
public class HomeController : Controller
{
// GET: Home
public ActionResult Index()
{
return View();
}
//[Route("Home/About")]
public ActionResult About()
{
return View();
}
//[Route("Home/ContactUs")]
public ActionResult ContactUs()
{
return View();
}
}
Index.cshtml
IndexPage
About.cshtml
AboutPage
Contactus.cshtml
ContactusPage
when I run the project then write the URL manually then also give output then why use the routing attribute
home/index
home/about
home/contactus
I comment the route attribute and custom route code and above URL give the proper output then why use route attribute
my question is without route attribute easily run the action method then why need to use route attribute above the controller

Answer 1

If you are happy with the default routes, then you don't need to use the route attributes, or put any custom routes in the RouteConfig.
You can add routes to customise how users get to your pages, either through parameters for more dynamic pages, or to make page urls more friendly - for example:
//make about us page url "/about"
routes.MapRoute(
name:"about",
url: "about",
defaults: new { controller = "Home",action= "About"}
);
//make a product page expect an id param in the url
//for example "/catalog/product/pid1"
//"/catalog/product/pid2"
//"/catalog/product/pid3"
//"/catalog/product/pid4" all match this route
routes.MapRoute(
name:"product",
url: "catalog/product/{productId}",
defaults: new { controller = "Catalog",action= "Product"}
);
The same can be achieved in route attributes:
[Route("about")]
public ActionResult AboutUs()
{
return View();
}
[Route("catalog/product/{productId}")]
public ActionResult GetProduct(string productId)
{
//Get product, build view data etc...
return View();
}