文件上传到阿里云

/// <summary>
        /// 文件上传
        /// </summary>
        /// <param name="file"></param>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public string FileSaveAliyunOSS(HttpPostedFileBase file, string fileName)
        {
            string FilePath = "";
            //上传到阿里云  
            using (Stream fileStream = file.InputStream)//转成Stream流  
            {
                string md5 = OssUtils.ComputeContentMd5(fileStream, file.ContentLength);
                //string today = DateTime.Now.ToString("yyyyMMdd");

                string extension = System.IO.Path.GetExtension(file.FileName);//扩展名 
                string FileName = Convert.ToString(Guid.NewGuid()).Replace("-", "") + extension;//文件名=文件名+当前上传时间  
                FilePath = fileName + "/" + Convert.ToString(DateTime.Now.Year) + "/" + Convert.ToString(DateTime.Now.Month) + "/" + FileName;//云文件保存路径  
                
                try
                {
                    //初始化阿里云配置--外网Endpoint、访问ID、访问password  
                    OssClient aliyun = new OssClient(endpoint, accessKeyId, accessKeySecret);

                    //将文件md5值赋值给meat头信息，服务器验证文件MD5  
                    var objectMeta = new ObjectMetadata
                    {
                        ContentMd5 = md5,
                        ContentType = "application/octet-stream",
                    };
                    //文件上传--空间名、文件保存路径、文件流、meta头信息(文件md5) //返回meta头信息(文件md5)  
                    PutObjectResult por = aliyun.PutObject(BucketName, FilePath, fileStream, objectMeta);
                    string text = por.ETag;
                    if (extension.ToUpper() == ".JPG")
                    {
                        FilePath += "-big";
                    }
                }
                catch (Exception e)
                {
                    ICE.Core.LogHelper.ErrorLog(log, string.Format("图片上传OSS出错了：{0}", Convert.ToString(e.Message)));
                    FilePath = "";
                }
            }
            return FilePath;
        }