HTTP-POST提交数据：ContentType=application/x-www-form-urlencoded 内容格式

//组合x-www-form-urlencoded格式的字符串
            var pdata = $"appid={appid}&nonce={nonce}&timestamp={timestamp}&sign={signStr}&operation=add&data={json}";

            //提交数据
            var result = WebApiTools.Post(url, pdata, "application/x-www-form-urlencoded;charset=UTF-8");
            return Newtonsoft.Json.JsonConvert.DeserializeObject<PostResult>(result);