What is it?
Routing, in ASP.NET, is the process of directing HTTP requests to endpoints, using the Middleware Pipeline to process and decide the endpoint.
Typically, all configuration of routing is made inside the Middleware Pipeline.
Routing in ASP.NET MVC
We can define routing for Controllers, using default routing with the .UseRouting() and .MapDefaultControllerRoute() method.
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllersWithViews(); // Services needed for controllers
var app = builder.Build(); // Set-up middleware
app.UseDefaultFiles();
app.UseStaticFiles();
app.UseRouting(); // Adds route-matching
app.MapDefaultControllerRoute(); // Adds default routing
app.Run();Or, equivalently, one can specify the arguments:
app.MapControllerRoute( // Default arguments
name: "default",
pattern: "{controller=Home}/{action=Index}/{id}"
);Where the name is not used in the routing itself, and a pattern that describes what requests should match. If a request does not match the pattern, it will be ignored and typically, a HTTP 404 error will be returned.
The first segment {controller=Home} specifies that the first value represents a Controller, and if not specified, the HomeController will be used. Same goes to the second segment, {action=Index}, that specifies the action to be used, and maps the Index action if passed none. The third segment {id?} is an optional parameter, an represent the id variable used in the action.