原来是用的PutObject()方式上传文件的，但是当文件比较大的时候，总是报一个对方强制关闭连接导致上传失败。PS：公司的网比较渣，10MB的文件都传不上去，搜了下，说使用Multipart Upload方式上传比较好，经过一番折腾，终于搞定了。

使用的是Upload Part Copy拷贝上传上传的方式。

官方文档：http://docs.aliyun.com/?spm=5176.383663.9.6.tg4Xaf#/pub/oss/sdk/dotnet-sdk&multipart-upload

        /// <summary>

        /// 将文件保存到阿里云oss

        /// </summary>

        /// <param name="httpPostedFile">要保存的文件</param>

        /// <param name="path">保存的文件路径</param>

        /// <returns>上传文件的路径</returns>

        public string SaveFile(HttpPostedFile httpPostedFile, string path)

        {

            //http://docs.aliyun.com/?spm=5176.383663.9.6.tg4Xaf#/pub/oss/sdk/dotnet-sdk&multipart-upload

            string fileExt = Path.GetExtension(httpPostedFile.FileName);

            string fileName = Path.Combine(path, Common.GetRamCode() + fileExt);

            OssClient client = ALOssClient.GetInstance();

            var bucketName = "wlx-zhibo";

            var objectName = fileName;

            // 开始Multipart Upload

            var request = new InitiateMultipartUploadRequest(bucketName, fileName);

            var r = client.InitiateMultipartUpload(request);

            // 打印UploadId

            Console.WriteLine(r.UploadId);

            var partSize = 102400;

            var fileSize = httpPostedFile.ContentLength;

            var partCount = fileSize / partSize;

            if (fileSize % partSize != 0)

            {

                partCount++;

            }

            var partETags = new List<PartETag>();

            using (var inputStream = httpPostedFile.InputStream)

            {

                for (var i = 0; i < partCount; i++)

                {

                    var skipBytes = (long)partSize * i;

                    inputStream.Seek(skipBytes, 0);

                    var size = (partSize < fileSize - skipBytes) ? partSize : (fileSize - skipBytes);

                    var req = new UploadPartRequest(bucketName, objectName, r.UploadId)

                    {

                        InputStream = inputStream,

                        PartSize = size,

                        PartNumber = i + 1

                    };

                    var uploadPart = client.UploadPart(req);

                    partETags.Add(uploadPart.PartETag);

                }

            }

            var completeMultipartUploadRequest = new CompleteMultipartUploadRequest(bucketName, objectName, r.UploadId);

            foreach (var partETag in partETags)

            {

                completeMultipartUploadRequest.PartETags.Add(partETag);

            }

            var result = client.CompleteMultipartUpload(completeMultipartUploadRequest);

            return result.Location;

        }