Adding error handling

Author: dstrockis

TodoListWebApp/App_Start/Startup.Auth.cs

@@ -8,6 +8,7 @@
 using System;
 using System.Threading.Tasks;
 using TodoListWebApp.Utils;
+using Microsoft.IdentityModel.Protocols;
 
 namespace TodoListWebApp
 {
@@ -42,11 +43,19 @@ public void ConfigureAuth(IApplicationBuilder app)
                 options.PostLogoutRedirectUri = Configuration.Get("AzureAd:PostLogoutRedirectUri");
                 options.Notifications = new OpenIdConnectAuthenticationNotifications
                 {
-                    AuthorizationCodeReceived = OnAuthorizationCodeReceived
+                    AuthorizationCodeReceived = OnAuthorizationCodeReceived,
+                    AuthenticationFailed = OnAuthenticationFailed
                 };
             });
         }
 
+        private Task OnAuthenticationFailed(AuthenticationFailedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> notification)
+        {
+            notification.HandleResponse();
+            notification.Response.Redirect("/Home/Error?message=" + notification.Exception.Message);
+            return Task.FromResult(0);
+        }
+
         public async Task OnAuthorizationCodeReceived(AuthorizationCodeReceivedNotification notification)
         {
             // Acquire a Token for the Graph API and cache it.  In the TodoListController, we'll use the cache to acquire a token to the Todo List API

TodoListWebApp/Controllers/HomeController.cs

@@ -26,8 +26,9 @@ public IActionResult Contact()
             return View();
         }
 
-        public IActionResult Error()
+        public IActionResult Error(string message)
         {
+            ViewBag.Message = message;
             return View("~/Views/Shared/Error.cshtml");
         }
     }

TodoListWebApp/Views/Shared/Error.cshtml

@@ -3,4 +3,6 @@
 }
 
 <h1 class="text-danger">Error.</h1>
-<h2 class="text-danger">An error occurred while processing your request.</h2>
+<h2 class="text-danger">We're having trouble signing you in.</h2>
+
+@ViewBag.Message