Default attribute routing not worrking in ASP.NET MVC

I'm trying to use attribute routing in my application. I provided the route attributes to all action methods and also provided the HTTP verbs to the action methods. But I am not able to set the default routing. If I manually provided the route in the URL, it's working but not able to see by default on application running. I used the empty [route("")] attribute for default.

Controller code :

namespace WebApplication2.Controllers
{
    [RoutePrefix("myproject")]
    public class AttributerouteController : Controller
    {
        // GET: Attributeroute
        [HttpGet]
        [Route("")]
        public ActionResult Employees()
        {
            return View();
        }

        [HttpGet]
        [Route("Employees/{id}")]
        public ActionResult Employeebyid(int id)
        {
            return View();
        }

        [HttpGet]
        [Route("Employees/{id}/department")]
        public ActionResult Empdepartment(int id)
        {
            return View();
        }
    }
}

My routeconfig.cs code :

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapMvcAttributeRoutes();
    //routes.RouteExistingFiles = true;
    routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Attributeroute", action = "Employees", id = UrlParameter.Optional }
    );
}

Use a tilde ~ on the method attribute to override the route prefix if needed:

[RoutePrefix("myproject")]  
public class AttributerouteController : Controller
{         
    [Route("~/")] 
    public ActionResult Employees()
    {
        return View();
    }                    

    [Route("Employees/{id}")] //http://localhost:12345/myproject/Employees/66           
    public ActionResult Employeebyid(int id)
    {
        //return View(nameof(Employees));
    }
  
    [Route("Employees/{id}/department")] // http://localhost:12345/myproject/Employees/66777/department     
    public ActionResult Empdepartment(int id)
    {
        //return View(nameof(Employees));
    }
}

By the way, you can omit the HttpGet attribute on the action methods. It is the default HTTP verb.

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An additional useful information you can find on the Microsoft blog, here: Attribute Routing in ASP.NET MVC 5