var virpath1 = "/upload/video/";
                string dirFullPath1 = Server.MapPath(virpath1);
                var video = VideoHelper.GetProductVideoUrl(dirFullPath1, virpath1, model.video, videoName);


public static string GetProductVideoUrl(string dirFullPath, string virpath, byte[] model, string qrCode)
        {
            if (model == null)
            {
                return "";
            }
            else
            {
                if (!Directory.Exists(dirFullPath))//如果資料夾不存在，則先建立資料夾
                {
                    Directory.CreateDirectory(dirFullPath);
                }
                var fileName = qrCode;
                dirFullPath = dirFullPath + fileName;
                if (!File.Exists(dirFullPath))
                {
                    SaveToVideo(dirFullPath, model);
                }
                var url = WebConfigurationManager.AppSettings["hostUrl"].ToString();
                return url + virpath + fileName;
            }
        }

        private static void SaveToVideo(string path, byte[] bytes)
        {
            FileStream fs = new FileStream(path, FileMode.CreateNew);
            fs.Write(bytes, 0, bytes.Length);
            fs.Close();
        }