使用任务库的 Amazon S3 异步上传答案

【问题标题】：Amazon S3 Async Upload using Task library使用任务库的 Amazon S3 异步上传
【发布时间】：2013-09-19 01:18:27
【问题描述】：

我有一个将文件上传到 Amazon S3 的 Windows 表单。我尝试实现内置异步方法，但似乎无法正常工作，所以我认为最好的方法是实现 System.Threading.Tasks。

我的实际代码如下所示：

public void UploadFileAsync(string bucketName, CloudDocument doc, bool publicRead)
{
config = new AmazonS3Config();
            config.CommunicationProtocol = Protocol.HTTP;
            client = Amazon.AWSClientFactory.CreateAmazonS3Client(accessKeyID, secretAccessKeyID, config);

// Load stream from file location
            FileMode mode = FileMode.Open;
            using (FileStream fs = new FileStream(doc.FullName, mode, FileAccess.Read))
            {
                // Create put object request
                TransferUtilityUploadRequest objectRequest = new TransferUtilityUploadRequest();
                objectRequest.InputStream = fs;
                objectRequest.BucketName = bucketName;

                if (publicRead) objectRequest.CannedACL = S3CannedACL.PublicRead;

                objectRequest.Key = doc.KeyName + doc.FileName.Replace(' ', '_');

                objectRequest.UploadProgressEvent += new EventHandler<UploadProgressArgs>(UploadProgressEvent);

                transferUtility = new TransferUtility(client);
                IAsyncResult asyncResult = transferUtility.BeginUpload(objectRequest, new AsyncCallback(UploadCallBack), results);

                waitHandles.Add(asyncResult.AsyncWaitHandle);



                // Wait till all the requests that were started are completed.
                WaitHandle.WaitAll(waitHandles.ToArray());
            }

            client.Dispose();

        }

}
private void UploadProgressEvent(object sender, UploadProgressArgs e)
        {
            if (UploadProgressChanged != null)
                UploadProgressChanged(this, e);
        }

private void UploadCallBack(IAsyncResult result)
        {

            Results results = result.AsyncState as Results;
            try
            {

                // If there was an error during the put attributes operation it will be thrown as part of the EndPutAttributes method.
                transferUtility.EndUpload(result);

                results.Successes++;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                results.Errors++;
            }
        }

有没有人尝试实现 Await / Async Task 以将异步上传到 amazon s3？

【问题讨论】：

究竟是什么不起作用？这段代码有什么作用？
异步，UI被阻塞了一会儿。

标签： c# amazon-s3 task-parallel-library async-await

【解决方案1】：

您可以在 MSDN 上找到wrapping APM and EAP members into TAP members 的说明。

总而言之，您使用Task.Factory.FromAsync 包装Begin/End 方法对，如下所示：

public static Task UploadAsync(this TransferUtility @this, TransferUtilityUploadRequest request)
{
    return Task.Factory.FromAsync(@this.BeginUpload, @this.EndUpload, request, null);
}

那么你可以这样使用它：

var task = transferUtility.UploadAsync(objectRequest);
tasks.Add(task);
await Task.WhenAll(tasks);

【讨论】：

我收到一个错误：由于 'AmazonS3Utility.UploadAsync(Amazon.S3.Transfer.TransferUtility, Amazon.S3.Transfer.TransferUtilityUploadRequest)' 是返回 'Task' 的异步方法，因此必须返回关键字后面不能跟对象表达式。您是否打算返回“Task”？
更新为非async 方法。
现在错误消失了。我必须将所有上传代码放在哪里？非常感谢。

【解决方案2】：

您可能还对AWS SDK 2.0 for .NET 的开发者预览版感兴趣。 TransferUtility 的异步扩展类的源代码可以在here 找到。如果您对预览有任何反馈，请告诉我们！

谢谢！

【讨论】：