How to get MVC action to return 404

Question

In ASP.NET MVC 3 and above you can return a HttpNotFoundResult from the controller.

return new HttpNotFoundResult("optional description");

There are multiple ways to do it,

1. You are right in common aspx code it can be assigned in your specified way
2. throw new HttpException(404, "Some description");

In MVC 4 and above you can use the built-in HttpNotFound helper methods:

if (notWhatIExpected)
{
    return HttpNotFound();
}

or

if (notWhatIExpected)
{
    return HttpNotFound("I did not find message goes here");
}

Code :

if (id == null)
{
  throw new HttpException(404, "Your error message");//RedirectTo NoFoundPage
}

Web.config

<customErrors mode="On">
  <error statusCode="404" redirect="/Home/NotFound" />
</customErrors>

If you are working with .NET Core, you can return NotFound()

I've used this:

Response.StatusCode = 404;
return null;

In NerdDinner eg. Try it

public ActionResult Details(int? id) {
    if (id == null) {
        return new FileNotFoundResult { Message = "No Dinner found due to invalid dinner id" };
    }
    ...
}