c#调用百度AI通用物体和场景识别

public class AdvancedGeneral
    {
        // 通用物体和场景识别
        public static AdvancedGeneralModel advancedGeneral(string token)
        {
            //string token = "[调用鉴权接口获取的token]";
            //通用物体和场景识别接口
            string host = "https://aip.baidubce.com/rest/2.0/image-classify/v2/advanced_general?access_token=" + token;
            Encoding encoding = Encoding.Default;
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(host);
            request.Method = "post";//请求方式
            request.KeepAlive = true;
            // 图片的base64编码
            string base64 = getFileBase64("c://cc.jpg");
            String str = "image=" + HttpUtility.UrlEncode(base64);
            byte[] buffer = encoding.GetBytes(str);
            request.ContentLength = buffer.Length;
            request.GetRequestStream().Write(buffer, 0, buffer.Length);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
            string result = reader.ReadToEnd();
            //Console.WriteLine("通用物体和场景识别:");
            //Console.WriteLine(result);

            AdvancedGeneralModel advancedGeneralModel = JsonConvert.DeserializeObject<AdvancedGeneralModel>(result);

            return advancedGeneralModel;
        }

        /// <summary>
        /// 把图片转化成base64格式
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static String getFileBase64(String fileName)
        {
            FileStream filestream = new FileStream(fileName, FileMode.Open);
            byte[] arr = new byte[filestream.Length];
            filestream.Read(arr, 0, (int)filestream.Length);
            string baser64 = Convert.ToBase64String(arr);
            filestream.Close();
            return baser64;
        }
    }

model:

    public class AdvancedGeneralModel
    {
        public List<SubAdvancedGeneralModel> result { get; set; }
    }

    public class SubAdvancedGeneralModel
    {
        public string root { get; set; }
        public string keyword { get; set; }
    }