Error Handling

1<system.web>
2  <customErrors mode="On" />            <!-- On | RemoteOnly | Off -->
3</system.web>
4<system.webServer>
5  <httpErrors existingResponse="PassThrough" />
6</system.webServer>

1<!-- Web.config -->
2<?xml version="1.0" encoding="utf-8"?>
3<configuration>
4  <appSettings>
5    <add key="webpages:Version" value="3.0.0.0" />
6    <add key="webpages:Enabled" value="false" />
7  </appSettings>
8  <system.web>
9    <compilation debug="false" targetFramework="4.8" />
10    <httpRuntime targetFramework="4.8" />
11    <customErrors mode="On" />
12  </system.web>
13  <system.webServer>
14    <httpErrors existingResponse="PassThrough" />
15  </system.webServer>
16</configuration>
17

18// Global.asax.cs
19using System;
20using System.Diagnostics;
21using System.Web;
22using System.Web.Mvc;
23using System.Web.Routing;
24using ShopSite.Controllers;
25

26namespace ShopSite
27{
28    public class MvcApplication : HttpApplication
29    {
30        protected void Application_Start()
31        {
32            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);   // adds HandleErrorAttribute
33            RouteConfig.RegisterRoutes(RouteTable.Routes);
34        }
35

36        // Last line of defence: everything MVC did not handle ends up here
37        protected void Application_Error()
38        {
39            var exception = Server.GetLastError();
40            var status = (exception as HttpException)?.GetHttpCode() ?? 500;
41            Trace.TraceError("Unhandled {0}: {1}", status, exception);     // use your logger here
42

43            if (status != 404) return;                                     // customErrors handles the rest
44

45            Server.ClearError();
46            Response.Clear();
47            Response.TrySkipIisCustomErrors = true;
48            var route = new RouteData();
49            route.Values["controller"] = "Error";
50            route.Values["action"] = "NotFound";
51            IController controller = new ErrorController();
52            controller.Execute(new RequestContext(new HttpContextWrapper(Context), route));
53        }
54    }
55}
56

57// Controllers/ErrorController.cs
58using System.Web.Mvc;
59

60namespace ShopSite.Controllers
61{
62    public class ErrorController : Controller
63    {
64        public ActionResult NotFound()
65        {
66            Response.StatusCode = 404;
67            Response.TrySkipIisCustomErrors = true;
68            return View();
69        }
70    }
71}
72

73// Controllers/ShopController.cs
74using System;
75using System.Web.Mvc;
76

77namespace ShopSite.Controllers
78{
79    public class ShopController : Controller
80    {
81        public ActionResult Crash()
82        {
83            throw new InvalidOperationException("Connection to SQL-PROD-01 failed for table dbo.Payments");
84        }
85

86        [HandleError(ExceptionType = typeof(TimeoutException), View = "Busy")]
87        public ActionResult Slow()
88        {
89            throw new TimeoutException("Payment gateway timed out");
90        }
91    }
92}
93

94@* Views/Shared/Error.cshtml *@
95@model HandleErrorInfo
96@{ ViewBag.Title = "Error"; }
97<h1>Sorry, something went wrong.</h1>
98<p>We have been notified. (Failed in @Model.ControllerName.@Model.ActionName)</p>
99

100@* Views/Shared/Busy.cshtml *@
101@{ ViewBag.Title = "Busy"; }
102<h1>We are very busy right now</h1>
103<p>Please try again in a minute.</p>
104

105@* Views/Error/NotFound.cshtml *@
106@{ ViewBag.Title = "Not found"; }
107<h1>Page not found</h1>
108<p><a href="/">Back to the shop</a></p>

GET /Shop/Crash
500 Internal Server Error
<h1>Sorry, something went wrong.</h1>
<p>We have been notified. (Failed in Shop.Crash)</p>

GET /Shop/Slow
500 Internal Server Error
<h1>We are very busy right now</h1>
<p>Please try again in a minute.</p>

GET /Shop/Missing
404 Not Found
<h1>Page not found</h1>
<p><a href="/">Back to the shop</a></p>

GET /nothing/here
404 Not Found
<h1>Page not found</h1>
<p><a href="/">Back to the shop</a></p>