.Net SDK 云对象存储示例代码 下载对象，下载的文件未能正常关闭，异步回调死锁导致进程占用

[levi930]

// 初始化 TransferConfig
TransferConfig transferConfig = new TransferConfig();

// 初始化 TransferManager
TransferManager transferManager = new TransferManager(cosXml, transferConfig);

String bucket = "examplebucket-1250000000"; //存储桶，格式：BucketName-APPID
String cosPath = "exampleobject"; //对象在存储桶中的位置标识符，即称对象键
string localDir = System.IO.Path.GetTempPath();//本地文件夹
string localFileName = "my-local-temp-file"; //指定本地保存的文件名

// 下载对象
COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, cosPath,
localDir, localFileName);

downloadTask.progressCallback = delegate (long completed, long total)
{
Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
};

try {
COSXML.Transfer.COSXMLDownloadTask.DownloadTaskResult result = await
transferManager.DownloadAsync(downloadTask);
Console.WriteLine(result.GetResultInfo());
string eTag = result.eTag;
} catch (Exception e) {
Console.WriteLine("CosException: " + e);
}

代码运行完成后，下载的资源文件会被进程占用，排查回调死锁导致FileStream未关闭

[konakonall]

是不是其他操作导致的？async/await 只是封装了封装的语法糖而已，本身并没有导致文件流不关闭

[levi930]

async/await 可不是封装的语法糖而已，必须 要理解 异步调用时的上下文环境。
不好意思，没认真看代码，刚开始以为是异步任务被阻塞，导致文件关闭的代码未被执行，
昨天仔测试了下代码，问题在于你的代码流程有问题，你这个代码回调风格写的不忍直视，httpclient封装啥的，过于设计。
COSXML.Network.ResponseBody类的AsyncStreamCallback此方法存在的问题
// responseBodyState.endResponseBody(false, ex)；
private void AsyncStreamCallback(IAsyncResult ar)
{
ResponseBodyState responseBodyState = ar.AsyncState as ResponseBodyState;

        Stream inputStream = responseBodyState.inputStream;

        try
        {
            int recvLen = inputStream.EndRead(ar);

            responseBodyState.completed += recvLen;

            System.Diagnostics.Debug.Print(this.isDownload+ ":读取到"+recvLen);
            if (recvLen > 0)
            {

                if (isDownload)
                {
                    fileStream.Write(responseBodyState.buffer, 0, recvLen);

                    if (progressCallback != null)
                    {
                        progressCallback(responseBodyState.completed, contentLength);
                    }
                }
                else
                {
                    memoryStream.Write(responseBodyState.buffer, 0, recvLen);
                }

                inputStream.BeginRead(responseBodyState.buffer, 0, responseBodyState.buffer.Length, AsyncStreamCallback, responseBodyState);
            }
            else

if (recvLen == 0)
{

                if (isDownload)
                {
                    fileStream.Flush();
                }
                else
                {

                    if ("application/xml".Equals(contentType, StringComparison.OrdinalIgnoreCase) &&
                        memoryStream.Length > 0 && memoryStream.Length < 10 * 1000)
                    {
                        memoryStream.Seek(0, SeekOrigin.Begin);
                        rawContentBodyString = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray());
                    }

                    memoryStream.Seek(0, SeekOrigin.Begin);
                    parseStream(memoryStream, contentType, responseBodyState.completed);
                }
               //此调用会结束当前任务，会导致调用当前异步的任务不会继续等待    此调用应该放在文件流关闭后面
                responseBodyState.endResponseBody(true, null);
               //若当前任务结束，后续代码不会执行
                responseBodyState.Clear();
               
                if (fileStream != null)
                {
                    fileStream.Close();
                    fileStream.Dispose();
                }

                if (memoryStream != null)
                {
                    memoryStream.Close();
                    memoryStream.Dispose();
                }

          
            }
        }
        catch (Exception ex)
        {
             //此处未测试，从流程上看也会有问题
            responseBodyState.endResponseBody(false, ex);
            responseBodyState.Clear();

            if (fileStream != null)
            {
                fileStream.Close();
                fileStream.Dispose();
            }

            if (memoryStream != null)
            {
                memoryStream.Close();
                memoryStream.Dispose();
            }

            QLog.Error("ResponseBody", ex.Message, ex);
        }

    }