WebClient.DownloadFileAsync下载服务器上的文件

问题描述：

我下载从远程位置的文件，以我的本地机器。我使用的路径保存在web.config中并在格式如下：

I am downloading a file from a remote location to my local machine. The paths I am using are saved in web.config and are in following format:

<add key="FileFolder" value="Files/"/>
<add key="LocalFileFolder" value="D:\REAL\" />

在code我使用的是下载：

the code I am using to download is:

  CreateDirectoryIfDoesNotExist();
  WebClient webClient = new WebClient();
  webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(webClient_DownloadFileCompleted);
  webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
  webClient.DownloadFileAsync(new Uri(context.Server.MapPath(ConfigurationManager.AppSettings["FileFolder"].ToString() + myfilename)), ConfigurationManager.AppSettings["LocalFileFolder"].ToString() + myfilename);

当我在服务器上部署;并运行我的程序，我得到一个消息，说下载已成功完成。但问题是，该文件在filefolder（LocalFileFolder）在服务器机器上下载。我希望它可以在本地计算机上下载。它是什么，我做错了？

When i deploy it on the server; and run my program, i get a message saying that download has completed successfully. But the problem is that the file is downloaded on the server machine in the filefolder (LocalFileFolder). I want it to be downloaded on the local machine. What is it that I am doing wrong?

答

你在做什么错的是正在运行在服务器上的这个code。如果这是一个Web应用程序（我猜那是因为你正在使用的HttpContext），你需要以流式传输文件的响应，而不是使用Web客户端。然后，用户在得到他的浏览器下载对话框，选择文件保存的地方，他希望（你不能覆盖此）。

What you are doing wrong is that you are running this code on the server. If this is a web application (I guess it is because you are using HttpContext) you need to stream the file to the response instead of using WebClient. Then the user gets a download dialog in his browser and chooses to save the file wherever he wants (you cannot override this).

所以：

context.Response.ContentType = "text/plain";
context.Response.AppendHeader("Content-Disposition", "attachment; filename=foo.txt");
context.Response.TransmitFile(@"d:\pathonserver\somefile.txt");

或者，你可以写你在客户机上运行，它使用Web客户端从远程服务器位置下载文件的桌面应用程序（WPF，WinForms的）。

Or you could write a desktop application (WPF, WinForms) which you run on the client machine and which uses WebClient to download a file from a remote server location.

WebClient.DownloadFileAsync下载服务器上的文件

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