Name types of Action Results in Web API 2

A Web API controller action can return any of the following:

• void – Return empty 204 (No Content)
• HttpResponseMessage – Return empty 204 (No Content)
• IHttpActionResult – Call ExecuteAsync to create an HttpResponseMessage, then convert to an HTTP response message
• Some other type – Write the serialized return value into the response body; return 200 (OK).