Error 500 instead of 404

Question

I have an asp.net MVC 5 project and I'm trying to throw a 404 error instead of 500.

The errors are

A public action method 'something' was not found on controller 'ProjetX.Controllers.HomeController'

and

The controller for path '/something' was not found or does not implement IController

I understand why it's an error 500 but I would like to throw a 404. It would be better for SEO.

I can't figure out how to

Here's my code

My ExceptionHandler class for elmah

public class HandleCustomError : HandleErrorAttribute
    {

        public override void OnException(ExceptionContext filterContext)
        {
            //If the exeption is already handled we do nothing
            if (filterContext.ExceptionHandled)
            {
                return;
            }
            else
            {
                //Log the exception with Elmah
                Log(filterContext);

                Type exceptionType = filterContext.Exception.GetType();

                //If the exception is while an ajax call
                if (exceptionType == typeof(ExceptionForAjax))
                {
                    filterContext.HttpContext.Response.Clear();
                    filterContext.HttpContext.Response.ContentEncoding = Encoding.UTF8;
                    filterContext.HttpContext.Response.HeaderEncoding = Encoding.UTF8;
                    filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
                    filterContext.HttpContext.Response.StatusCode = 500;
                    filterContext.HttpContext.Response.StatusDescription = filterContext.Exception.Message;
                }
                else
                {
                    base.OnException(filterContext);
                }

            }

            //Make sure that we mark the exception as handled
            filterContext.ExceptionHandled = true;
        }

        private void Log(ExceptionContext context)
        {
            // Retrieve the current HttpContext instance for this request.
            HttpContext httpContext = context.HttpContext.ApplicationInstance.Context;

            if (httpContext == null)
            {
                return;
            }

            // Wrap the exception in an HttpUnhandledException so that ELMAH can capture the original error page.
            Exception exceptionToRaise = new HttpUnhandledException(message: null, innerException: context.Exception);

            // Send the exception to ELMAH (for logging, mailing, filtering, etc.).
            ErrorSignal signal = ErrorSignal.FromContext(httpContext);
            signal.Raise(exceptionToRaise, httpContext);
        }

    }

How I add the custom errors

public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            filters.Add(new HandleCustomError());
        }

The routes config

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

            routes.MapRoute("Robots.txt",
                "robots.txt",
                new { controller = "robot", action = "index" });

            routes.MapRoute(
                name: "Localization",
                url: "{lang}/{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
                constraints: new { lang = @"^[a-zA-Z]{2}$" }

            );

            routes.MapRoute(
                name: "Default",
                url: "{controller}/{action}/{id}",
                defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
            );

       routes.MapRoute(
        "NotFound",
        "{*url}",
        new { controller = "Error", action = "Error404" }
        );


            routes.MapMvcAttributeRoutes();
        }

My webconfig

<system.web>
    <authentication mode="None" />
    <compilation debug="true" targetFramework="4.5" />
    <!-- 2MB-->
    <httpRuntime targetFramework="4.5" maxRequestLength="2097152" />
    <httpModules>
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" />
      <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" />
    </httpModules>
    <!-- Set mode to RemoteOnly in production -->
    <customErrors mode="On" redirectMode="ResponseRewrite" defaultRedirect="/Error/Error500">
      <error statusCode="400" redirect="/Error/Error400" />
      <error statusCode="404" redirect="/Error/Error404" />
      <error statusCode="500" redirect="/Error/Error500" />
    </customErrors>
  </system.web>
  <system.webServer>
    <httpErrors errorMode="Custom" existingResponse="Replace">
      <remove statusCode="400" subStatusCode="-1" />
      <error statusCode="400" path="/Error/Error400" responseMode="ExecuteURL" />
      <remove statusCode="404" subStatusCode="-1" />
      <error statusCode="404" path="/Error/Error404" responseMode="ExecuteURL" />
      <remove statusCode="500" subStatusCode="-1" />
      <error statusCode="500" path="/Error/Error500" responseMode="ExecuteURL" />
    </httpErrors>
    <modules>
      <remove name="FormsAuthenticationModule" />
      <add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" preCondition="managedHandler" />
      <add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" preCondition="managedHandler" />
    </modules>
    <validation validateIntegratedModeConfiguration="false" />
    <handlers>
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <remove name="OPTIONSVerbHandler" />
      <remove name="TRACEVerbHandler" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
      <add name="Robots-ISAPI-Integrated-4.0" path="/robots.txt" verb="GET" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
    <staticContent>
    </staticContent>
  </system.webServer>

I wanted to handle the error in the HandleCustomError class but the problem is that it goes straight to my Error500 action in the error controller.

What's weird is that the error is still logged in elmah.

It doesn't hit any breakpoint inside the HandleCustomError class, how can the error be logged?

Thank you

You can't return a 404 in the Error500 action in the error controller? — Robert Harvey, Mar 23 '15 at 15:42
How do I know if it's a real 500 error or those 2 specific errors in the error controller? — Marc, Mar 23 '15 at 15:43
I see 404 and 500. You say you want to replace 500 with 404. So...? — Robert Harvey, Mar 23 '15 at 15:46
A public action method 'something' was not found on controller 'ProjetX.Controllers.HomeController' throws a 500 but I would prefer a 404 — Marc, Mar 23 '15 at 15:47
Swap it with 404 in the Error500 action in the error controller. — Robert Harvey, Mar 23 '15 at 15:47
If a server-side method is not implemented, why throw a client-side error? — MakePeaceGreatAgain, Mar 23 '15 at 15:48
@HimBromBeere this error happens when someone types a wrong url. it should be a 404. no? — Marc, Mar 23 '15 at 15:49
So you provide the name of the function to be called within the url, right? And this function may or may not be implementing leading to the mentioned error? — MakePeaceGreatAgain, Mar 23 '15 at 15:51
What you really need to do is fix the problem that's causing the 500 error. — Robert Harvey, Mar 23 '15 at 15:52
I tried ``routes.MapRoute( "NotFound", "{*url}", new { controller = "Error", action = "Error404" } );`` but it didn't change anything — Marc, Mar 23 '15 at 15:53
@HimBromBeere Yes, mvc tries to find a controller that match the url. — Marc, Mar 23 '15 at 15:54
I'm not sure how to verify that. It goes straight to the error 500 and it tells me theres no controller that match the request — Marc, Mar 23 '15 at 15:56
This also looks helpful: http://stackoverflow.com/questions/4001081/asp-net-mvc-catch-all-route-and-default-route — Robert Harvey, Mar 23 '15 at 16:00
Thank you Robert, the second link works like a charm. You can write this as an answer. I will add my code also — Marc, Mar 23 '15 at 16:49
@RobertHarvey Don't forget to write your answer to get your points — Marc, Mar 25 '15 at 19:29

score 1 · Accepted Answer · edited May 23 '17 at 12:28

Here's the final code that works

I had to add 2 functions to generate a regex with all the name of my controllers and actions

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


        routes.MapRoute(
            name: "Localization",
            url: "{lang}/{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional },
            constraints: new { lang = @"^[a-zA-Z]{2}$", controller = GetAllControllersAsRegex(), action = GetAllActionsAsRegex }

        );

        routes.MapRoute(
            "Default",
            "{controller}/{action}/{id}",
            new { controller = "Home", action = "Index", id = UrlParameter.Optional },
            new { controller = GetAllControllersAsRegex(), action = GetAllActionsAsRegex() }
        );

        routes.MapRoute(
        "NotFound",
        "{*url}",
        new { controller = "Error", action = "Error404" }
        );

        routes.MapMvcAttributeRoutes();
    }
    private static string GetAllControllersAsRegex() 
    { 
        var controllers = typeof(MvcApplication).Assembly.GetTypes()
            .Where(t => t.IsSubclassOf(typeof(Controller))); 

        var controllerNames = controllers
            .Select(c => c.Name.Replace("Controller", "")); 

        return string.Format("({0})", string.Join("|", controllerNames)); 
    }
    private static string GetAllActionsAsRegex()
    {
        Assembly asm = Assembly.GetExecutingAssembly();

        var actions = asm.GetTypes()
                        .Where(type => typeof(Controller).IsAssignableFrom(type)) //filter controllers
                        .SelectMany(type => type.GetMethods())
                        .Where(method => method.IsPublic && !method.IsDefined(typeof(NonActionAttribute)))
                        .Select(x=>x.Name);

        return string.Format("({0})", string.Join("|", actions)); 
    }
}

See Also
https://stackoverflow.com/a/4668252

Could you write your comment about the catch-all route as an answer, I will give you the points plz — Marc, Mar 25 '15 at 22:00
This doesn't look like the catchall route played much of a part in the solution. — Robert Harvey, Mar 25 '15 at 22:03

Error 500 instead of 404

1 Answers1