Routing ASP.NET Core 5 - default value of id always returns 0

Question

I have a project in ASP.NET Core 5, what I need is quite simple. I want to indicate in the id value a default int value in routing. However, when I trace the controller, it always returns the id as 0 or null.

public IActionResult Seccion(int id)
{
   
    return View();
}

this is my Start.up file

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

            endpoints.MapControllerRoute(
                        name: "historias",
                        pattern: "seccion/{id=300}",
                        defaults: new { controller = "Podcast", action = "Seccion" });

        });

As you can see, I expect when the https://localhost:xxx/podcast/seccion/historias is entered the Seccion() action method is called with id set to 300 by default. But the id always arrives 0.

Answer 1

Your problem caused by wrong routes registration order (conventional routing is order-dependent). It is important that you add "historias" route before the Default one. Routes are processed in the order they are listed. So, define routes in the following order:

app.UseEndpoints(endpoints =>
        {      
            endpoints.MapControllerRoute(
                        name: "historias",
                        pattern: "{controller}/seccion/historias/{id=300}",
                        defaults: new { controller = "Podcast", action = "Seccion" });

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

And the "historias" route template does not include the controller name. Therefore it is necessary to use the following URL: https://localhost:port/seccion or https://localhost:port/seccion/[some_number_here].

Pay attention! When you are using http://localhost:port/podcast/seccion the "default" route template is engaged and therefore the id is 0.

But, if you will define the default id value in the action method like public IActionResult Seccion(int id=300) the following URL's https://localhost:port/podcast/seccion or https://localhost:port/podcast/seccion/[some_number_here] will properly work too.

For more information see Set up conventional route

Answer 2

you should set your default value in Action

public IActionResult Seccion(int id = 300)
{
   
    return View();
}

when call https://localhost:xxx/podcast/seccion id is 300 and when call https://localhost:xxx/podcast/seccion/1 id is 1

for more information read this