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

Ravi Vishwakarma 662 12 Jun 2025

Ravi Vishwakarma

IT-Hardware & Networking

Ravi Vishwakarma is a dedicated Software Developer with a passion for crafting efficient and innovative solutions. With a keen eye for detail and years of experience, he excels in developing robust software systems that meet client needs. His expertise spans across multiple programming languages and technologies, making him a valuable asset in any software development project.

1 Answers

Ravi Vishwakarma 12 Jun 2025

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 ≥ 1
You 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 APIs
When URL structure is custom or non-standard
To improve readability and local control over routes

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