e.g. 3.14 Checking for Form Validation Errors

chap3_your_first_mvc_app/PartyInvites/Controllers/HomeController.cs

@@ -37,8 +37,16 @@ namespace PartyInvites.Controllers
         [HttpPost]
         public ActionResult RsvpForm(GuestResponse guestResponse)
         {
-            // TODO: Email guestResponse to the part organizer
+            if (ModelState.IsValid)
-            return View("Thanks" ,guestResponse);
+            {
+                // TODO: Email guestResponse to the part organizer
+                return View("Thanks", guestResponse);
+            }
+            else
+            {
+                // there is a validation error - redisplay the for
+                return View();
+            }
         }
     }
 }