Action route optional id parameter

Question

I'm trying to create a controller action with optional /id parameter like so:

1. default http://localhost/tasks
2. with id http://localhost/tasks/42

Here is the controller and the action: What I tried to do was to use the route attribute on the action

public class TasksController : AsyncController
{
    [Route("tasks/{id}")]
    public ActionResult Index(string id)
    {
        ...
    }
}

This worked but only with the id parameter set in the url, but the default page /tasks throws a not found error, alternatively when using [Route("tasks")] without the id, the default page works, but when id is set, a not found error is thrown again. I also tried [Route("tasks/{id ?}")] to mark the id as optional parameter but it didn't work.

Any ideas how to make this work?

Answer 1

You can make a URI parameter optional by adding a question mark to the route parameter. If a route parameter is optional, you must define a default value for the method parameter.

Set the default value on the action method and add question mark to end of route param.

[Route("tasks/{id?}")]
public ActionResult Index(string id =null)