How does routing work in ASP.NET MVC? Explain attribute routing.

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ICSM Computer · Answer

How Routing Works in ASP.NET MVC
Routing in ASP.NET MVC maps incoming URL requests to
controller actions. It decouples the URL structure from the physical file paths, allowing
clean, user-friendly URLs.
1. Conventional Routing
Defined in RouteConfig.cs (usually in App_Start folder):
public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",  // pattern
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );
    }
}
Example URL Matching:
URL
Controller
Action
ID
/Home/Index
Home
Index
null
/Product/Details/5
Product
Details
5
2. Attribute Routing
Instead of defining routes globally, you place route attributes directly on controllers and actions.
Enable it (usually in RouteConfig.cs):
public static void RegisterRoutes(RouteCollection routes)
{
    routes.MapMvcAttributeRoutes(); // Enable attribute routing
    // You can still keep conventional routes
    routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
    );
}
Example: Using Attribute Routing
public class ProductsController : Controller
{
    [Route("products/list")]
    public ActionResult List()
    {
        return View();
    }
    [Route("products/details/{id:int}")]
    public ActionResult Details(int id)
    {
        return View();
    }
}
This maps:
/products/list → ProductsController.List()/products/details/10 → ProductsController.Details(10)
Advanced Attribute Routing
Optional Parameters
[Route("blog/{year:int}/{month:int?}")]
public ActionResult Archive(int year, int? month)
Matches /blog/2025 and /blog/2025/06
Route Names and Constraints
[Route("orders/{id:int:min(1)}", Name = "OrderDetails")]
public ActionResult Details(int id)
Only matches if id is an integer ≥ 1You can use Url.RouteUrl("OrderDetails", new { id = 5 }) to generate the URL
Summary: Conventional vs Attribute Routing
Feature
Conventional Routing
Attribute Routing
Defined in
RouteConfig.cs
On controllers/actions
Centralized
Yes
No
Fine-grained control
Harder
Easier
Preferred for
Standard patterns
RESTful APIs, specific URLs
When to Use Attribute Routing
For RESTful APIsWhen URL structure is custom or non-standardTo improve readability and local control over routes

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How does routing work in ASP.NET MVC? Explain attribute routing.

ICSM Computer

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1 Answers

How Routing Works in ASP.NET MVC

1. Conventional Routing

Example URL Matching:

2. Attribute Routing

Enable it (usually in `RouteConfig.cs`):

Example: Using Attribute Routing

This maps:

Advanced Attribute Routing

Optional Parameters

Route Names and Constraints

Summary: Conventional vs Attribute Routing

When to Use Attribute Routing

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URL	Controller	Action	ID
`/Home/Index`	Home	Index	null
`/Product/Details/5`	Product	Details	5

Feature	Conventional Routing	Attribute Routing
Defined in	RouteConfig.cs	On controllers/actions
Centralized	Yes	No
Fine-grained control	Harder	Easier
Preferred for	Standard patterns	RESTful APIs, specific URLs