public ActionResult Index(string version = null)
    {
    if (!string.IsNullOrWhiteSpace(version))
        {
            if (version == "V1")
                return View("Index", new HomeViewModel
                {
                    Version = settingsProvider.CurrentApiVersion
                });
            if (version == "V2")
                return View("AngularApp");
        }
        return View("AngularApp");
   }

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

        //enable attribute routing
        routes.MapMvcAttributeRoutes();

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
            constraints: new
            {
                serverRoute = new ServerRouteConstraint(url =>
                    {
                        return !url.PathAndQuery.StartsWith("/App-", StringComparison.InvariantCultureIgnoreCase);
                    })
            }
        );

        routes.MapRoute(
            name: "angular",
            url: "{*url}",
            defaults: new {controller = "Home", action = "Index"});
    }
}

const routes: Routes = [
      {path: '', redirectTo: 'App-Documentation', pathMatch: 'full'}
      ,
      {
          path: '',
          component: LayoutComponent,
          children: [
    {
      path: '',
      component: DocumentationComponent
    },
    {
      path: 'App-Documentation',
      component: DocumentationComponent
    },
    {
      path: 'App-Settings',
      component: AdministrationComponent
    },
    {
      path: 'App-Chat',
      component: ChatComponent
    }
  ]
   },
    { path: '**', redirectTo: 'App-Documentation' }
  ];

[RoutePrefix("")]
public class ClientApiController : ApiBaseController
{

serverRoute = new ServerRouteConstraint(url =>
                    {
                        return !url.PathAndQuery.StartsWith("/App-", StringComparison.InvariantCultureIgnoreCase);
                    })

routes.MapRoute(
            name: "angular",
            url: "{*url}",
            defaults: new {controller = "Home", action = "Index"});

{ path: '**', redirectTo: 'App-Documentation' }