ASP.NET MVC - How to throw a 404 page similar to that on StackOverflow

Question

I've currently got a BaseController class that inherits from System.Web.Mvc.Controller. On that class I have the HandleError Attribute that redirects users to the "500 - Oops, we screwed up" page. This is currently working as expected.

THIS WORKS

<HandleError()> _
Public Class BaseController : Inherits System.Web.Mvc.Controller
''# do stuff
End Class

I also have my 404 pages working on a Per-ActionResult basis which is again working as expected.

THIS WORKS

 Function Details(ByVal id As Integer) As ActionResult
 Dim user As Domain.User = UserService.GetUserByID(id)
 If Not user Is Nothing Then
 Dim userviewmodel As Domain.UserViewModel = New Domain.UserViewModel(user)
 Return View(userviewmodel)
 Else
 ''# Because of RESTful URL's, some people will want to "hunt around"
 ''# for other users by entering numbers into the address. We need to
 ''# gracefully redirect them to a not found page if the user doesn't
 ''# exist.
 Response.StatusCode = CInt(HttpStatusCode.NotFound)
 Return View("NotFound")
 End If
 End Function

Again, this works great. If a user enters something like http://example.com/user/999 (where userID 999 doesn't exist), they will see the appropriate 404 page, and yet the URL will not change (they are not redirected to an error page).

I CAN'T GET THIS IDEA TO WORK

Here's where I'm having an issue. If a user enters http://example.com/asdf- they get kicked over to the generic 404 page. What I want to do is leave the URL in tact (IE: not redirect to any other page), but simply display the "NotFound" view as well as push the HttpStatusCode.NotFound to the client.

For an example, just visit https://stackoverflow.com/asdf where you'll see the custom 404 page and see the URL left in tact.

Obviously I'm missing something, but I can't figure it out. Since "asdf" doesn't actually point to any controller, my base controller class isn't kicking in, so I can't do it in the "HandleError" filter in there.

Thanks in advance for the help.

Note: I absolutely do not want to redirect the user to a 404 page. I want them to stay at the existing URL, and I want MVC to push the 404 VIEW to the user.

Edit:

I have also tried the following to no avail.

Shared Sub RegisterRoutes(ByVal routes As RouteCollection)
 routes.RouteExistingFiles = False
 routes.IgnoreRoute("{resource}.axd/{*pathInfo}")
 routes.IgnoreRoute("Assets/{*pathInfo}")
 routes.IgnoreRoute("{*robotstxt}", New With {.robotstxt = "(.*/)?robots.txt(/.*)?"})
 routes.AddCombresRoute("Combres")
 ''# MapRoute allows for a dynamic UserDetails ID
 routes.MapRouteLowercase("UserProfile", _
 "Users/{id}/{slug}", _
 New With {.controller = "Users", .action = "Details", .slug = UrlParameter.Optional}, _
 New With {.id = "\d+"} _
 )
 ''# Default Catch All Valid Routes
 routes.MapRouteLowercase( _
 "Default", _
 "{controller}/{action}/{id}/{slug}", _
 New With {.controller = "Events", .action = "Index", .id = UrlParameter.Optional, .slug = UrlParameter.Optional} _
 )
 ''# Catch All InValid (NotFound) Routes
 routes.MapRoute( _
 "NotFound", _
 "{*url}", _
 New With {.controller = "Error", .action = "NotFound"})
End Sub

My "NotFound" route is doing nothing.

Answer 1

Found my answer on my other SO question. Thanks very much Anh-Kiet Ngo for the solution.

protected void Application_Error(object sender, EventArgs e)
{
 Exception exception = Server.GetLastError();
 // A good location for any error logging, otherwise, do it inside of the error controller.
 Response.Clear();
 HttpException httpException = exception as HttpException;
 RouteData routeData = new RouteData();
 routeData.Values.Add("controller", "YourErrorController");
 if (httpException != null)
 {
 if (httpException.GetHttpCode() == 404)
 {
 routeData.Values.Add("action", "YourErrorAction");
 // We can pass the exception to the Action as well, something like
 // routeData.Values.Add("error", exception);
 // Clear the error, otherwise, we will always get the default error page.
 Server.ClearError();
 // Call the controller with the route
 IController errorController = new ApplicationName.Controllers.YourErrorController();
 errorController.Execute(new RequestContext(new HttpContextWrapper(Context), routeData));
 }
 }
}

• Paul: This is a good solution however before errorController.Execute(new RequestContext(new HttpContextWrapper(Context), routeData)); is called, this line needs to be added Response.StatusCode = 404; If this line is not added, the page response is still a 200 regardless of what is rendered for the user.
• Cameron Taggart: IController.Execute is protected, at least in MVC 4, so I just had to expose it wrap it from my controller: public void Exec(RequestContext requestContext) { this.Execute(requestContext); }

Answer 2

You could try :

<customErrors mode="On" redirectMode="ResponseRewrite">
 <error statusCode="404" redirect="~/Error.aspx"/>
</customErrors>

http://msdn.microsoft.com/en-us/library/system.web.configuration.customerrorssection.redirectmode.aspx

If the RedirectMode property is set to ResponseRewrite, the user is sent to error page and the original URL in the browser is not changed.

• Keith: ResponseRewrite has issues sometimes if the error is in a WebForms page and the redirect is an MVC one and vice versa.
• Raul Vejar: @Keith, could you expand on this? I'm running into these cases and I want to try to understand why it only works some times...
• Keith: @RaulVejar not really, this is an old post (I think the problem was with MVC2) and we just avoided it with different custom errors for MVC and WebForms
• Raul Vejar: @Keith, hate to say it but there is still issues in MVC4. We had to end up handling errors manually on the global asax and turn of custom errors completely

Answer 3

Routes are pattern matches. Your not found route isn't working because the pattern of your incorrect URL matches an earlier route.

So:

''# Default Catch All Valid Routes
routes.MapRouteLowercase( _
 "Default", _
 "{controller}/{action}/{id}/{slug}", _
 New With {.controller = "Events", .action = "Index", .id = UrlParameter.Optional, .slug = UrlParameter.Optional} _
)
''# Catch All InValid (NotFound) Routes
routes.MapRoute( _
 "NotFound", _
 "{*url}", _
 New With {.controller = "Error", .action = "NotFound"})

If you enter: http://example.com/asdf- then that matches the "Default" route above - MVC goes looking for asdf-Controller and can't find it, so exception thrown.

If you go to http://example.com/asdf-/action/id/slug/extra then "Default" no longer matches and the "NotFound" route will be followed instead.

You could add a filter for all your known controllers to the "Default" route, but that's going to be a pain to maintain when you add new controllers.

You shouldn't need to hook into the Application_Error event at all, but I haven't found a better way around the missing controller yet - I asked it as another question.

Answer 4

I got this to work by simply returning the action defined in the base controller, rather than redirecting to it.

[HandleError]
public ActionResult NotFound()
{
 Response.StatusCode = 404;
 Response.TrySkipIisCustomErrors = true; 
 return View("PageNotFound", SearchUtilities.GetPageNotFoundModel(HttpContext.Request.RawUrl)); 
}

(The "SearchUtilities.GetPageNotFoundModel" bit is about generating suggestions by feeding the URL into our search engine)

In any action method that inherits the base, I can simply call this:

return NotFound();

... whenever I catch an invalid parameter. And the catch-all route does the same.

• Chase Florell: This is ok, but I'm now able to do it without the need for a NotFound action. Makes things much cleaner.
• Faust: I see. That's appealing. How do you deal with routes that get matched, therefore don't throw 404, but get passed invalid parameters?
• Chase Florell: I have a custom HandleNotFoundException that I can throw from a valid controller. It will load up the appropriate shared view Shared/NotFound.cshtml but still keep the URI intact. throw HandleNotFoundException
• Chase Florell: My answer above is out of date... I need to update it with my solution.

Answer 5

Set it up in the web config:

<system.web>
 <customErrors mode="On" defaultRedirect="error.html"/>
</system.web>

error.html is your custom page that you can have to display any arbitrary HTML to the user.

• Chase Florell: Like I said, I do NOT want to redirect the user.
• Chris Kooken: What if you set up a route in the routing dictionary that had unknown routes route to your error controller/actionresult and returned the view you wanted. That would leave the URL in tact.
• Chase Florell: hmm, what would a route like that look like?
• Chase Florell: -1 because the answer "Redirects" which is precisely what I DON'T want.

Answer 6

It's big miss from ASP.NET MVC framework because you can't customize (real customization I mean not just-one-error-page-for-anything) 404 pages without "crunches" like 1 answer. You can use one 404 error for all not-found causes, or you can customize multiple 500 error pages via [HandleError], but you CAN NOT customize 404 errs declaratively. 500 errs are bad due to SEO reasons. 404 errs are good errs.