How do I return NotFound() IHttpActionResult with an error message or exception?

Question

I am returning a NotFound IHttpActionResult, when something is not found in my WebApi GET action. Along with this response, I want to send a custom message and/

Answer 1

Here's a one-liner for returning a IHttpActionResult NotFound with a simple message:

return Content(HttpStatusCode.NotFound, "Foo does not exist.");