Q:

Dynamic routing action name in ASP.NET MVC

I would like to create a dynamic routing to a URL like following:
http://localhost:51577/Item/AnyActionName/Id

Please note that the controller name is static and doesn't need to be dynamic. On the other hand, I need to have the action name part dynamic so that whatever is written in that part of URL, I would redirect the user to the Index action inside of Item controller.
What I have tried so far is:
public static void RegisterRoutes(RouteCollection routes)
{
    routes.MapRoute(
        "Items",
        "Item/{action}/{id}",
        new { controller = "Item", action = "Index",  id = UrlParameter.Optional });
}

And when I build my app I get a following error:

The resource cannot be found.

Edit:
Here is my Global.asax file and the routeconfig.cs file:
public class MvcApplication : System.Web.HttpApplication
{

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
    }
}

And here's the content of the RouteConfig.cs file with the answer that @Nkosi provided:
public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );

        routes.MapRoute(
            name: "Items",
            url: "Item/{id}/{*slug}",
            defaults: new { controller = "Item", action = "Index", slug = UrlParameter.Optional }
        );
    }
}

A:

What you are referring to in your question is called a slug. 
I answered a similar question here for web api
Web api - how to route using slugs?
With the slug at the end the route config would look like this
public static void RegisterRoutes(RouteCollection routes) {

    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapRoute(
        name: "Items",
        url: "Item/{id}/{*slug}",
        defaults: new { controller = "Item", action = "Index", slug = RouteParameter.Optional }
    );

    routes.MapRoute(
        name: "Default",
        url: "{controller}/{action}/{id}",
        defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
    );

}

which could match an example controller action...
public class ItemController : Controller {
    public ActionResult Index(int id, string slug = null) {
        //...
    }
}

the example URL...
"Item/31223512/Any-Item-Name"

would then have the parameters matched as follows...

id = 31223512
slug = "Any-Item-Name"

And because the slug is optional, the above URL will still be matched to
"Item/31223512"

