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Routing to Controller Actions in ASP.NET Core

Introduction

In ASP.NET Core, routing plays a pivotal role in directing incoming HTTP requests to the appropriate controller actions, enabling developers to build powerful and structured web applications.

This article will delve into the fundamentals of routing in ASP.NET Core, illustrating how to configure routes to map URLs to specific controller actions with detailed examples.

Routing in ASP.NET Core

  • Routing in ASP.NET Core refers to the process of determining how an incoming request should be handled and which controller action should be invoked based on the URL and other request attributes.
  • The routing mechanism in ASP.NET Core is highly flexible and configurable, allowing developers to define custom routes to suit their application's requirements.

Defining Controller and Actions

Before configuring routing, it's essential to create controllers and define action methods within them. Each action method represents a distinct endpoint in the application. Here's an example of a simple controller with two action methods:

public class HomeController : Controller
{
    public IActionResult Index()
    {
        return View();
    }

    public IActionResult About()
    {
        return View();
    }
}

In this example, the HomeController contains two action methods: Index() and About(), which correspond to the /Home/Index and /Home/About URLs, respectively.

Configuring Routing

Routing configuration in ASP.NET Core is typically done in the Startup.cs file within the Configure method.

The UseEndpoints method is used to define the routing rules. Let's examine how to configure routing for our example controller:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Other middleware configurations

    app.UseRouting();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute(
            name: "default",
            pattern: "{controller=Home}/{action=Index}/{id?}");
    });
}

In the MapControllerRoute method

  • name: Specifies the name of the route.
  • pattern: Defines the URL pattern to match, consisting of placeholders for the controller, action, and optional parameters.
  • {controller=Home}: Specifies the default controller to be used if no controller is specified in the URL.
  • {action=Index}: Specifies the default action to be used if no action is specified in the URL.
  • {id?}: Defines an optional parameter named id.

Accessing the Action

With routing configured, ASP.NET Core's routing system matches incoming requests to the appropriate controller and action method based on the defined routes. For instance:

  • A request to /Home/Index will invoke the Index action method of the HomeController.
  • A request to /Home/About will invoke the About action method of the HomeController.

Attribute Routing (Optional)

In addition to convention-based routing, ASP.NET Core supports attribute routing, allowing developers to define routes directly on controller actions or controllers using attributes.

Here's an example

[Route("api/[controller]")]
public class ValuesController : ControllerBase
{
    [HttpGet]
    public IActionResult Get()
    {
        // Action logic
    }

    [HttpPost]
    public IActionResult Post([FromBody] SomeModel model)
    {
        // Action logic
    }
}

In this example, all actions in the ValuesController would be prefixed with /api/values.

Conclusion

Routing is a crucial aspect of building web applications in ASP.NET Core, enabling developers to map incoming requests to specific controller actions efficiently. By understanding the fundamentals of routing and how to configure routes in ASP.NET Core, developers can create well-structured and easily navigable web applications. Whether using convention-based routing or attribute routing, ASP.NET Core offers flexibility and versatility in defining routes to suit diverse application requirements.


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