public IActionResult FilterKeys([FromQuery] string field, int index = 1) { try { if (field == null || field.Equals("")) { var res1 = _keysService.GetUnique1stFields(); if (res1 == null) { return(NotFound()); } return(Ok(res1)); } var res2 = _keysService.GetUniqueNextFields(field, index); if (res2 == null) { return(NotFound()); } return(Ok(res2)); } catch (Exception e) { return(BadRequest(e)); } }