在浏览器中从FTP下载文件

 1     public static class FTPHelper
 2     {
 3         /// <summary>
 4         /// 得到特定FTP目录的文件列表
 5         /// </summary>
 6         /// <param name="uri">ftp://{username}:{password}@ftp.baidu.com/{folderName}</param>
 7         public static List<String> ListFiles(Uri serverUri)
 8         {
 9             // The serverUri parameter should start with the ftp:// scheme.
10             if (serverUri.Scheme != Uri.UriSchemeFtp)
11             {
12                 throw new ArgumentException("uri must be ftp scheme");
13             }
14 
15             FtpWebRequest ftpRequest = null;
16             StreamReader reader = null;
17             try
18             {
19                 // Get the object used to communicate with the server.
20                 ftpRequest = (FtpWebRequest)FtpWebRequest.Create(serverUri);
21 
22                 ftpRequest.Method = WebRequestMethods.Ftp.ListDirectory;
23 
24                 reader = new StreamReader(ftpRequest.GetResponse().GetResponseStream(), Encoding.Default);
25 
26                 //read data.
27                 List<String> fileNames = new List<String>();
28                 string line = reader.ReadLine();
29                 while (line != null)
30                 {
31 
32                     fileNames.Add(line);
33                     line = reader.ReadLine();
34                 }
35 
36                 return fileNames;
37 
38             }
39             catch(Exception ex)
40             {
41                 throw ex;
42             }
43             finally
44             { 
45               if(reader != null)
46               {
47                   reader.Close();
48               }
49               if (ftpRequest != null)
50               {
51                   ftpRequest.Abort();
52               }
53             }
54         }
55 
56         /// <summary>
57         /// 得到特定文件的大小
58         /// </summary>
59         /// <param name="uri">ftp://{username}:{password}@ftp.baidu.com/{fileName}</param>
60         public static long GetFileSize(Uri serverUri)
61         {
62             // The serverUri parameter should start with the ftp:// scheme.
63             if (serverUri.Scheme != Uri.UriSchemeFtp)
64             {
65                 throw new ArgumentException("uri must be ftp scheme");
66             }
67 
68             FtpWebRequest ftpRequest = null;
69             StreamReader reader = null;
70             try
71             {
72                 // Get the object used to communicate with the server.
73                 ftpRequest = (FtpWebRequest)FtpWebRequest.Create(serverUri);
74 
75                 ftpRequest.Method = WebRequestMethods.Ftp.GetFileSize;
76 
77                 return ftpRequest.GetResponse().ContentLength;
78             }
79             catch (Exception ex)
80             {
81                 throw ex;
82             }
83             finally
84             {
85                 if (reader != null)
86                 {
87                     reader.Close();
88                 }
89                 if (ftpRequest != null)
90                 {
91                     ftpRequest.Abort();
92                 }
93             }
94         }
95     }

        /// <summary>
        /// 下载文件（此方法定义在实现Controller某类的某个MVC Controller中）
        /// </summary>
        /// <param name="uri"></param>
        public void DownLoadFile(Uri uri,string fileName)
        {
            //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
            {
                long fileSize = FTPHelper.GetFileSize(uri);
                //Create a WebRequest to get the file
                FtpWebRequest fileReq = (FtpWebRequest)FtpWebRequest.Create(uri);

                //Create a response for this request
                FtpWebResponse fileResp = (FtpWebResponse)fileReq.GetResponse();

                //Get the Stream returned from the response
                stream = fileResp.GetResponseStream();

                // prepare the response to the client. resp is the client Response
                var resp = HttpContext.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", fileSize.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();
                }
            }
        }