c# object轉string

JObject patientinfo = new JObject();
patientinfo["start_time"] = kssj;
patientinfo["end_time"] = jssj;
patientinfo["device_ids"] = device_ids;
patientinfo["threshold"] = 15;
patientinfo["top_k"] = 10;
patientinfo["algorithm_vendors"] = algorithm_vendors;
patientinfo["image"] = usermacs[0]["MACJH"].ToString();
string sendData = JsonConvert.SerializeObject(patientinfo);