Use MapSpaFallbackRoute in ReactServices and demo

samples/react/ReactGrid/Controllers/HomeController.cs

@@ -1,11 +1,10 @@
-using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc;
 
 namespace ReactExample.Controllers
 {
     public class HomeController : Controller
     {
-        public IActionResult Index(int pageIndex)
+        public IActionResult Index()
         {
             return View();
         }

samples/react/ReactGrid/Startup.cs

@@ -58,9 +58,8 @@ namespace ReactExample
             // Add MVC to the request pipeline.
             app.UseMvc(routes =>
             {
-                routes.MapRoute(
+                routes.MapSpaFallbackRoute(
                     name: "default",
-                    template: "{pageIndex?}",
                     defaults: new { controller="Home", action = "Index" });
             });
         }