Request.CreateResponse in asp.net core

Finally I make a solution. :)

[HttpPost]
public HttpResponseMessage AddBusinessUsersToBusinessUnit(MyObject request)
{
    return new HttpResponseMessage(HttpStatusCode.Unauthorized);
}

If you just want to return a status code, the following is preferable

//Creates a StatusCodeResult object by specifying a statusCode.
//so controller method should return IActionResult 
return StatusCode(HttpStatusCode.Unauthorized)

See more in this SO answer