.NET MVC throws 500 Server Error instead of 404 Not Found when cannot match a Controller path

Question

For some reason, when entering a dud URL to a file/directory/controller that does not exist, the following error is thrown:

System.Web.HttpException The controller for path '' was not found or does not implement IController System.Web.Mvc.IController > GetControllerInstance(System.Web.Routing.RequestContext, System.Type)

IIS then follows the regular error handling and shows the page appropriate for a 500 Internal Server Error. A 404 Not Found error handling logic should be followed. Another web application I am testing on DOES NOT throw this HttpException when it can't find a route, and returns 404 normally. So what triggeres this HttpException?

Why and how to follow a 404 route for this type of error instead of a 500? Below is the configuration of the error handling. No other code is handling errors. So why is the 500 error always shown. It's as if the default handling handles the 'can't find controller' exception as an error when in fact it's a not-found.

<system.webServer> <httpErrors errorMode="Custom" existingResponse="Replace" defaultPath="/StaticErrors/Default.html" defaultResponseMode="ExecuteURL"> <clear /> <error statusCode="404" path="/mvcError/Http404" responseMode="ExecuteURL" /> <error statusCode="500" path="/mvcError/Http500" responseMode="ExecuteURL" /> </httpErrors> </system.webServer> <system.web> <customErrors defaultRedirect="/StaticErrors/Default.html" mode="On" redirectMode="ResponseRewrite"> <error redirect="/mvcError/Http404" statusCode="404" /> <error redirect="/mvcError/Http500" statusCode="500" /> </customErrors> </system.web>

Failed Request Trace shows this. Basically since no route is round, the HttpException is thrown, and the 500 route handling kicks in, instead of a 404. I'm not doing anything to overide any normal default behaviour. The HandleErrorAttribute is not being added either to the MVC filters.

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Perhaps give us an example of a URL that produces the undesirable message. — Andrew Shepherd
– Andrew Shepherd, Commented Aug 18, 2014 at 5:08
Have you tried [This][1] [1]: stackoverflow.com/questions/5385714/… — Amol
– Amol, Commented Aug 18, 2014 at 5:08
Questions seeking debugging help ("why isn't this code working?") must include the desired behavior, a specific problem or error and the shortest code necessary to reproduce it. You should provide all your route maps. — Erik Philips
– Erik Philips, Commented Aug 18, 2014 at 5:46
@ErikPhilips The question does include the desired behavior. This isn't a why the code doesn't work query. It's a how does one reflect a route not found exception as a HTTP 404 instead of a HTTP 500... The routes are irrelevant, as I'm not hitting a route, hence the exception. This is simply using a new project in Visual Studio and the web.config changed to above. — simbolo
– simbolo, Commented Aug 18, 2014 at 5:50
The only way to change the error code is to catch the exception and change the http status code in code. The web.config can't change http status codes to other status codes. — Erik Philips
– Erik Philips, Commented Aug 18, 2014 at 5:56

Hiệp Lê · Accepted Answer · 2014-08-18 10:18:11Z

1

You should add a filter controller to override some IIS custom error.

public class mvcErrorController : Controller { public ActionResult Http404() { Response.StatusCode = 404; Response.TrySkipIisCustomErrors = true; return View(); } }

edited Aug 18, 2014 at 10:18

answered Aug 18, 2014 at 9:40

Hiệp Lê

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2 Comments

Reporter Over a year ago

I think it would be more helpful for the OP and further visitors, when you add some explaination to your intension.

simbolo Over a year ago

I already have one code like this within the controller. And nothing else, trouble is, the Http500 method is the one that is always selected. So even throwing a HttpNotFoundException is literally treated by MVC as an unhandled exception and triggers the Http500 method. Strange!

Community · Accepted Answer · 2017-05-23 12:09:09Z

You need to remove the

redirectMode="ResponseRewrite"

Option from you customErrors tag. Unfortunately, this does mean you will have a 302 before your 404, but it will fix your issue.

Alternatively, use ASPX pages for your error pages:

<customErrors defaultRedirect="/StaticErrors/Default.html" mode="On" redirectMode="ResponseRewrite"> <error redirect="/StaticErrors/Http404.aspx" statusCode="404" /> <error redirect="/StaticErrors/Http500.aspx" statusCode="500" /> </customErrors>

There is previous discussion on this issue on SO here

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.NET MVC throws 500 Server Error instead of 404 Not Found when cannot match a Controller path

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