ASP.NET App routing for SPA

HomeController.cs

using System;
using System.Diagnostics;
using System.Security.Claims;
using System.Web.Mvc;

namespace ISS.OPF.API.Controllers
{
    // [Authorize] - you don't need authorization if all page auth is handled in frontend
    public class HomeController : Controller
    {
        {
            return new FilePathResult("~/index.html", "text/html"); // Point to the root file of the spa
        }
    }
}

RouteConfig.cs

using System.Web.Mvc;
using System.Web.Routing;

namespace Routing.App
{
    public class RouteConfig
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            // You can add routes for specific controllers if you need them
            routes.MapRoute(
                name: "Account",
                url: "account/{action}/{id}",
                defaults: new { controller = "Account", action = "Index", id = UrlParameter.Optional }
            );

            // Catchall route - 404s will be handled in frontend app
            // This will make the app return the result from
            // Homecontrollers Index method on all routes not specified above
            routes.MapRoute(
                "Default",
                "{*catchall}",
                new { controller = "Home", action = "Index" }
            );
        }
    }
}