从URL下载/流文件-asp.net

  • Z时代
  • 2024-01-10
  • 分类：问答

我需要流式传输文件，这将导致在浏览器中保存为提示。问题是，该文件所在的目录已虚拟映射，因此我无法使用Server.MapPath确定其实际位置。该目录与网站不在同一位置（甚至不在实时服务器上）。

我想要类似以下的内容，但这将允许我传递Web URL，而不是服务器文件路径。

我可能最终不得不从配置基本路径构建我的文件路径，然后追加到路径的其余部分，但是希望我可以用这种方式来代替。

var filePath = Server.MapPath(DOCUMENT_PATH);
if (!File.Exists(filePath))
    return;
var fileInfo = new System.IO.FileInfo(filePath);
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", String.Format("attachment;filename=\"{0}\"", filePath));
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.WriteFile(filePath);
Response.End();

回答：

您可以使用HttpWebRequest获取文件并将其流回客户端。这使您可以获取带有URL的文件。我发现的一个示例（但不记得该在哪里归功）是

    //Create a stream for the file
    Stream stream = null;
    //This controls how many bytes to read at a time and send to the client
    int bytesToRead = 10000;
    // Buffer to read bytes in chunk size specified above
    byte[] buffer = new Byte[bytesToRead];
    // The number of bytes read
    try
    {
      //Create a WebRequest to get the file
      HttpWebRequest fileReq = (HttpWebRequest) HttpWebRequest.Create(url);
      //Create a response for this request
      HttpWebResponse fileResp = (HttpWebResponse) fileReq.GetResponse();
      if (fileReq.ContentLength > 0)
        fileResp.ContentLength = fileReq.ContentLength;
        //Get the Stream returned from the response
        stream = fileResp.GetResponseStream();
        // prepare the response to the client. resp is the client Response
        var resp = HttpContext.Current.Response;
        //Indicate the type of data being sent
        resp.ContentType = "application/octet-stream";
        //Name the file 
        resp.AddHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        resp.AddHeader("Content-Length", fileResp.ContentLength.ToString());
        int length;
        do
        {
            // Verify that the client is connected.
            if (resp.IsClientConnected)
            {
                // Read data into the buffer.
                length = stream.Read(buffer, 0, bytesToRead);
                // and write it out to the response's output stream
                resp.OutputStream.Write(buffer, 0, length);
                // Flush the data
                resp.Flush();
                //Clear the buffer
                buffer = new Byte[bytesToRead];
            }
            else
            {
                // cancel the download if client has disconnected
                length = -1;
            }
        } while (length > 0); //Repeat until no data is read
    }
    finally
    {
        if (stream != null)
        {
            //Close the input stream
            stream.Close();
        }
    }

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