public IHttpActionResult PostDepartment([FromBody] Department department) { try { var Departments = db.Departments.ToList(); if (Departments == null) //in case that there aren't any students on the db yet { Departments = new List <Department>(); } if (Departments.Exists(d => d.Id == department.Id)) //validates if the id written it's already on the db { return(NotFound()); //return response id it's incorrect } else { db.Departments.Add(department); } db.SaveChanges(); return(Ok()); } catch { return(InternalServerError()); //return response when there is an error adding an student } }