MVC 4 HttpNotFound() and 404 error

Question

I have a controller in which I am processing a part of the url and if it matches some criteria I will return a View but if not I will return a HttpNotFound().

Now I have set up a friendly 404 page which a user will be redirected to if a 404 is thrown so why doesn't the HttpNotFound redirect to this page?

I would expect the 404 to be thrown then the page to be redirected to the error page as set up in the web.config but it just shows the default 404 page. I have checked with other urls that don't exist and these all redirect to the proper error page

Answer 1

As it turns out you're meant to throw an exception:

throw new HttpException(404, "Page Not Found");

This seems to handle the 404 and then redirect you to the proper page rather than just the IIS 404 page

Answer 2

Just taking a guess...

The reason that you are not redirected to the friendly 404 page is because IIS/MVC were able to process the request. Then when processing the request you determine that you needed to return a 404 status code to the client.

Personally, I prefer to return a 404 status code and my PageNotFound view similar to this approach that is used by StackOverflow: https://stackoverflow.com/a/499907/84395