C# MVC 从 S3 异步下载大文件

我必须从 aws S3 async 下载文件。我有一个锚标记，单击它时，将在控制器中点击一个方法以供下载。该文件应该在浏览器底部开始下载，就像其他文件下载一样。

In View

<a href="/controller/action?parameter">Click here</a>

在控制器中

public void action()
{
     try
     {
           AmazonS3Client client = new AmazonS3Client(accessKeyID, secretAccessKey);
           GetObjectRequest req = new GetObjectRequest();
           req.Key = originalName;
           req.BucketName = ConfigurationManager.AppSettings["bucketName"].ToString() + DownloadPath;
           FileInfo fi = new FileInfo(originalName);
           string ext = fi.Extension.ToLower();
           string mimeType = ReturnmimeType(ext);
           var res = client.GetObject(req);
           Stream responseStream = res.ResponseStream;
           Stream response = responseStream;
           return File(response, mimeType, downLoadName);
     }
     catch (Exception)
     {
           failure = "File download failed. Please try after some time.";   
     }              
}

上述函数使浏览器加载直到文件完全下载。然后只有文件在底部可见。我看不到 mb 是如何下载的。
提前致谢。

您必须发送ContentLength向客户端显示进度。浏览器没有关于它将接收多少数据的信息。

如果你看一下来源FileStreamResult类，被使用File方法，它不会通知客户端有关“Content-Length”的信息。https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/FileStreamResult.cs https://aspnetwebstack.codeplex.com/SourceControl/latest#src/System.Web.Mvc/FileStreamResult.cs

替换这个，

return File(response, mimeType, downLoadName);

with

return new FileStreamResultEx(response, res.ContentLength, mimeType, downloadName);


public class FileStreamResultEx : ActionResult{

     public FileStreamResultEx(
        Stream stream, 
        long contentLength,         
        string mimeType,
        string fileName){
        this.stream = stream;
        this.mimeType = mimeType;
        this.fileName = fileName;
        this.contentLength = contentLength;
     }


     public override void ExecuteResult(
         ControllerContext context)
     {
         var response = context.HttpContext.Response; 
         response.BufferOutput = false;
         response.Headers.Add("Content-Type", mimeType);
         response.Headers.Add("Content-Length", contentLength.ToString());
         response.Headers.Add("Content-Disposition","attachment; filename=" + fileName);

         using(stream) { 
             stream.CopyTo(response.OutputStream);
         }
     }

}

选择

一般来说，从服务器下载和传送 S3 文件是一种不好的做法。您将向您的托管帐户收取两倍的带宽费用。相反，您可以使用签名 URL 来传递非公共 S3 对象，其生存时间只有几秒钟。你可以简单地使用预签名 URL

 public ActionResult Action(){
     try{
         using(AmazonS3Client client = 
              new AmazonS3Client(accessKeyID, secretAccessKey)){
            var bucketName = 
                 ConfigurationManager.AppSettings["bucketName"]
                .ToString() + DownloadPath;
            GetPreSignedUrlRequest request1 = 
               new GetPreSignedUrlRequest(){
                  BucketName = bucketName,
                  Key = originalName,
                  Expires = DateTime.Now.AddMinutes(5)
               };

            string url = client.GetPreSignedURL(request1);
            return Redirect(url);
         }
     }
     catch (Exception)
     {
         failure = "File download failed. Please try after some time.";   
     }              
 }

只要对象没有公共读取策略，未经签名的用户就无法访问对象。

另外，您必须使用using around AmazonS3Client为了快速处理网络资源，或者只使用一个静态实例AmazonS3Client这将减少不必要的分配和取消分配。