How to force a 404 Not Found Error

I built a CMS that works fine, when the article can be found in the database, but when the article has been deleted or the recordset is empty, I just want the web server's 404 Page Not Found page to appear.

I tried the response.statuscode = 404 and response.status = "Page Not Found", but neither or both did not work.
 I also tried,
throw New HttpException(0x194,"") but that didn't work either

Any hints would be great... Thank you,
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