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

Answers here are missing a little developer story problem. The ApiController class is still exposing a NotFound() method that developers may use. This would cause some 404 response to contain a uncontrolled result body.

I present here a few parts of code "better ApiController NotFound method" that will provide a less error-prone method that does not require developers to know "the better way of sending a 404".

• create a class inheriting from ApiController called ApiController
  • I use this technique to prevent developers from using the original class
• override its NotFound method to let devs use the first available api
• if you want to discourage this, mark this as [Obsolete("Use overload instead")]
• add an extra protected NotFoundResult NotFound(string message) that you want to encourage
• problem: the result does not support responding with a body. solution: inherit and use NegotiatedContentResult. see attached better NotFoundResult class.