[Authorize]
        [HttpPost("UploadSingleFile")]
        public async Task<string> Post(IFormFile photo, [FromHeader] string classId)
        {
            //string classId = "c333";
            if (photo == null)
            {
                return "No File Uploaded";
            }
            try
            {
                string fname = DoPhotoUpload(photo);
                string fullpath = Path.Combine(_env.WebRootPath, "photos/" + fname);

                string date = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
                Face[] faces = await UploadAndDetectFaces(fullpath);

                int faceId = 0;
                if (faces.Length != 0)
                {
                    var webPath = hostName + "/photos/" + fname;

                    string sql = @"INSERT INTO Image (ImageName, ImagePath,uploadTime, classId) VALUES
                        ('{0}','{1}','{2:yyyy-MM-dd HH:mm:ss}','{3}')";
                    if (DBUtl.ExecSQL(sql, fname, webPath, date, classId) == 1)
                    {
                        //await faceServiceClient.CreatePersonGroupAsync(classId, classId);

                        foreach (var face in faces)
                        {

                            Guid[] faceID = new Guid[1];
                            faceID[0] = face.FaceId;
                            string debug = face.FaceId.ToString();

                            var results = await faceServiceClient.IdentifyAsync(classId, faceID);
                            foreach (var identifyResult in results)
                            {
                                if (identifyResult.Candidates.Length != 0)
                                {
                                    var candidateId = identifyResult.Candidates[0].PersonId;
                                    var person = await faceServiceClient.GetPersonAsync(classId, candidateId);
                                    faceId = System.Convert.ToInt32(person.Name);
                                }
                            }
                            //store all the emotion data into different data
                            var Happiness = face.FaceAttributes.Emotion.Happiness;
                            var Sadness = face.FaceAttributes.Emotion.Sadness;
                            var Surprise = face.FaceAttributes.Emotion.Surprise;
                            var Fear = face.FaceAttributes.Emotion.Fear;
                            var Anger = face.FaceAttributes.Emotion.Anger;
                            var Contempt = face.FaceAttributes.Emotion.Contempt;
                            var Disgust = face.FaceAttributes.Emotion.Disgust;
                            var Neutral = face.FaceAttributes.Emotion.Neutral;
                            var FaceID = face.FaceId;
                            var Age = face.FaceAttributes.Age;
                            var Gender = face.FaceAttributes.Gender;
                            string sql1 = @"INSERT INTO Face(FaceId, studentId, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, ImageName)
                               VALUES('{0}',{1},{2},{3},{4},{5},{6},{7},{8},{9},'{10}')";
                            string sql2 = @"INSERT INTO Face(FaceId, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, ImageName)
                               VALUES('{0}',{1},{2},{3},{4},{5},{6},{7},{8},'{9}')";
                            int result = 0;
                            if (faceId == 0)
                            {
                                string debug22 = string.Format(sql2, FaceID, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, fname);
                                result = DBUtl.ExecSQL(sql2, FaceID, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, fname);

                            }
                            else
                            {
                                string debug11 = string.Format(sql1, FaceID, faceId, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, fname);
                                result = DBUtl.ExecSQL(sql1, FaceID, faceId, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, fname);
                            }


                            if (result != 1)

                            {
                                return "insert lesson fail" + DBUtl.DB_Message + String.Format(sql1, FaceID, faceId, Anger, Contempt, Disgust, Fear, Happiness, Neutral, Sadness, Surprise, fname);
                            }
                            returnValue rv = new returnValue(fname, faceId);
                            string value = JsonConvert.SerializeObject(rv);
                            if (faceId != 0)
                            {
                                markAttendance(faceId, classId);
                            }

                        }
                        if (faces.Length > 1)
                        {
                            return "Multi Entry";

                        }
                        else
                        {
                            return faceId.ToString();
                        }
                    }
                    else
                    {
                        return "insert image fail" + DBUtl.DB_Message + String.Format(sql, fname, fullpath, date, classId);
                    }

                }
                else
                {
                    return "No face detected!";
                }

            }
            catch (Exception ex)
            {
                return ex.Message;
            }
        }

        private string DoPhotoUpload(IFormFile photo)
        {
            string fext = ".jpg";
            string uname = Guid.NewGuid().ToString();
            string fname = uname + fext;
            string fullpath = Path.Combine(_env.WebRootPath, "photos/" + fname);
            using (FileStream fs = new FileStream(fullpath, FileMode.Create))
            {
                photo.CopyTo(fs);
            }
            return fname;
        }