RouteConfig.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Routing;

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

            //Маршрут для основного SPA приложения
            routes.MapRoute(
                name: "App",
                url: "{controller}/{action}",
                defaults: new { controller = "App", action = "Index"}
            );

            //Маршрут для web api
            routes.MapRoute(
                name: "Api",
                url: "api/{controller}/{action}/{id}",
                defaults: new { id = UrlParameter.Optional }
            );
        }
    }
}