Question

I have tried the following 2 things to have a page return a 404 error:

public ActionResult Index()
{
    return new HttpStatusCodeResult(404);
}

public ActionResult NotFound()
{
    return HttpNotFound();
}

but both of them just render a blank page. How can I manually return a 404 error from within ASP.NET MVC 3?

Answer 1

If you inspect the response using fiddler, I believe you’ll find that the blank page is in fact returning a 404 status code. The problem is no view is being rendered and thus the blank page.

You could get an actual view to be displayed instead by adding a customErrors element to your web.config that will redirect the user to a specific url when a certain status code occurs which you can then handle as you would with any url. Here’s a walk-through below:

First throw the HttpException where applicable. When instantiating the exception, be sure to use one of the overloads which takes a http status code as a parameter like below.

throw new HttpException(404, "NotFound");

Then add an custom error handler in your web.config file so that you could determine what view should be rendered when the above exception occurs. Here’s an example below:

<configuration>
    <system.web>
        <customErrors mode="On">
          <error statusCode="404" redirect="~/404"/>
        </customErrors>
    </system.web>
</configuration>

Now add a route entry in your Global.asax that’ll handle the url “404” which will pass the request to a controller’s action that’ll display the View for your 404 page.

Global.asax

routes.MapRoute(
    "404", 
    "404", 
    new { controller = "Commons", action = "HttpStatus404" }
);

CommonsController

public ActionResult HttpStatus404()
{
    return View();
}

All that’s left is to add a view for the above action.

One caveat with the above method: according to the book “Pro ASP.NET 4 in C# 2010” (Apress) the use of customErrors is outdated if you’re using IIS 7. Instead you should use the httpErrors section. Here’s a quote from the book:

But although this setting still works with Visual Studio’s built-in test web
server, it’s effectively been replaced by the <httpErrors> section in IIS 7.x.