"Cannot close stream until all bytes are written" WriteAsync 操作取消时

Question

当取消对 HttpWebRequest.GetRequestStream() 创建的流的 WriteAsync 操作时，我收到一个 WebException，其中包含以下消息：

Cannot close stream until all bytes are written

当我使用 CancellationToken 取消操作时，如何清理我的 HttpWebRequest 和流？

这是我的工作代码的一部分（我为此 post 清理了一些 headers 所以请求可能格式不正确）：

    public async Task<bool> UploadAsync(FileInfo fi, CancellationToken ct, IProgress<int> progress = null)
    {
        FileStream fs = new FileStream(fi.FullName, FileMode.Open);
        int bufferSize = 1 * 1024 * 1024;
        byte[] buffer = new byte[bufferSize];
        int len;
        long position = fs.Position;
        long totalWrittenBytes = 0;
        HttpWebRequest uploadRequest = null;
        Stream putStream = null;
        try
        {
            while ((len = fs.Read(buffer, 0, buffer.Length)) > 0)
            {

                uploadRequest = (HttpWebRequest)WebRequest.Create("http://myuploadUrl");
                uploadRequest.Method = "PUT";
                uploadRequest.AddRange(position, position + len - 1);
                uploadRequest.ContentLength = len;
                putStream = uploadRequest.GetRequestStream();

                int posi = 0;
                int bytesLeft = len;
                int chunkSize;
                while (bytesLeft > 0)
                {
                    chunkSize = Math.Min(25 * 1024, bytesLeft); //25KB
       //HERE IS the WriteAsync part that is being cancelled           
                    await putStream.WriteAsync(buffer, posi, chunkSize, ct);
                    bytesLeft -= chunkSize;
                    posi += chunkSize;
                    totalWrittenBytes += chunkSize;
                    if (progress != null)
                        progress.Report((int)(totalWrittenBytes * 100 / fs.Length));
                }

                putStream.Close();
                putStream = null;
                position = fs.Position;
                var putResponse = (HttpWebResponse)uploadRequest.GetResponse();
                putResponse.Close();
                uploadRequest = null;
            }

            //putStream.Write(buffer, 0, len);

        }
        catch (OperationCanceledException ex)
        { 
            if (putStream != null)
            {
                putStream.Flush();
                putStream.Close();//WebException occur here: Cannot close stream until all bytes are written.
            }    
        return false;
        }
        finally{
            fs.Close();
        }
        return true;
    }

Answer 1

我终于抓住了 WebException 因为 post 请求必须写入预期的字节数 (ContentLength 属性)

这是我的最后收获

        catch (OperationCanceledException ex)
        {
            try
            {
                if (putStream != null)
                    putStream.Dispose();
            }
            catch (WebException) { }
            return false;
        }
        finally{
            fs.Close();
        }

也许我不确定是否应该尝试处理流？

"Cannot close stream until all bytes are written" WriteAsync 操作取消时

"Cannot close stream until all bytes are written" when WriteAsync operation is Cancelled

c#

asynchronous

stream

httprequest

async-await