How to get MVC action to return 404

I have an action that takes in a string that is used to retrieve some data. If this string results in no data being returned (maybe because it has been deleted), I want to return a 404 and display an error page.

I currently just use return a special view that display a friendly error message specific to this action saying that the item was not found. This works fine, but would ideally like to return a 404 status code so search engines know that this content no longer exists and can remove it from the search results.

What is the best way to go about this?

Is it as simple as setting Response.StatusCode = 404?

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;

None of the above examples worked for me until I added the middle line below:

public ActionResult FourOhFour()
{
    Response.StatusCode = 404;
    Response.TrySkipIisCustomErrors = true; // this line made it work
    return View();
}

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" };
    }
    ...
}

In .NET Core 1.1:

return new NotFoundObjectResult(null);

I use:

Response.Status = "404 NotFound";

This works for me :-)

You can also do:

        if (response.Data.IsPresent == false)
        {
            return StatusCode(HttpStatusCode.NoContent);
        }

Please try the following demo code:

public ActionResult Test()

{
　　return new HttpStatusCodeResult (404,"Not found");
}