FTP Download

     最近要完成WPF程序的自动升级功能，自动升级的思路请见圣殿骑士的WPF企业内训全程实录(下)中的部署与自动更新 部分。其中就需要连接到FTP服务器进行文件的下载，查阅了 All-In-One Code Framework 的 CSFTPDownload 例子和微软的帮助文档。其中主要代码引用自CSFTPDownload和微软官方示例。详情请自己查阅微软官方MSDN，最好是安装到自己的电脑上，查阅起来方便，具体操作方法请参见英文VS2010安装中文版MSDN文档方法和VS2010帮助查看器推荐两片文章。

      这里使用 System.Net.FtpWebRequest 类通过编程的方式与FTP服务器进行交互。另外还可以使用 System.Net.WebClient 类来进行操作。

直接上代码，代码是可用的，经过测试通过的。

 

public class FTPHelper

    {

        public FTPHelper(NetworkCredential credentials)

        {

            this.Credentials = credentials;

        }



        #region Fields



        // 2M bytes.

        public const int MaxCacheSize = 2097152;



        // 2K bytes.

        public const int BufferSize = 2048;



        public NetworkCredential Credentials { get; set; }



        #endregion Fields



        #region Public Methods



        /// <summary>

        /// Download file. FTP Uri eg.ftp://localhost/TestDiretory/ (In this,Last '/' must be include)

        /// </summary>

        /// <param name="urlStr"></param>

        /// <param name="fileName"></param>

        /// <param name="savePath"></param>

        public  void DownloadFile(string urlStr, string fileName,string savePath)

        {



            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(urlStr + fileName);

            request.Method = WebRequestMethods.Ftp.DownloadFile;



            if (!Directory.Exists(savePath))

            {

                Directory.CreateDirectory(savePath);

            }



            string destPath = Path.Combine(savePath, fileName);



            request.Credentials = Credentials;



            FtpWebResponse response = null;

            Stream responseStream = null;

            MemoryStream downloadCache = null;



            try

            {

                response = (FtpWebResponse)request.GetResponse();



                responseStream = response.GetResponseStream();



                StreamReader reader = new StreamReader(responseStream);



                // Cache data in memory.

                downloadCache = new MemoryStream(MaxCacheSize);

                byte[] downloadBuffer = new byte[BufferSize];



                int bytesSize = 0;

                int cachedSize = 0;



                // Download the file until the download is completed.

                while (true)

                {



                    // Read a buffer of data from the stream.

                    bytesSize = responseStream.Read(downloadBuffer, 0,

                        downloadBuffer.Length);



                    // If the cache is full, or the download is completed, write 

                    // the data in cache to local file.

                    if (bytesSize == 0

                        || MaxCacheSize < cachedSize + bytesSize)

                    {

                        try

                        {

                            // Write the data in cache to local file.

                            WriteCacheToFile(downloadCache, destPath, cachedSize);



                            // Stop downloading the file if the download is paused, 

                            // canceled or completed. 

                            if (bytesSize == 0)

                            {

                                break;

                            }



                            // Reset cache.

                            downloadCache.Seek(0, SeekOrigin.Begin);

                            cachedSize = 0;

                        }

                        catch (Exception ex)

                        {

                            throw ex;

                        }



                    }



                    // Write the data from the buffer to the cache in memory.

                    downloadCache.Write(downloadBuffer, 0, bytesSize);

                    cachedSize += bytesSize;

                }

            }catch(Exception ex)

            {

                throw new Exception("下?载?文?件t失§败ü！?",ex);

            }

            finally

            {

                if (response != null)

                {

                    response.Close();

                }



                if (responseStream != null)

                {

                    responseStream.Close();

                }



                if (downloadCache != null)

                {

                    downloadCache.Close();

                }

            }

        }







        #endregion Public Methods



        #region Private Methods



        /// <summary>

        /// Write the data in cache to local file.

        /// </summary>

        private void WriteCacheToFile(MemoryStream downloadCache, string downloadPath,

            int cachedSize)

        {

            using (FileStream fileStream = new FileStream(downloadPath,

                FileMode.Create))

            {

                byte[] cacheContent = new byte[cachedSize];

                downloadCache.Seek(0, SeekOrigin.Begin);

                downloadCache.Read(cacheContent, 0, cachedSize);

                fileStream.Write(cacheContent, 0, cachedSize);

            }

        }



        #endregion Private Methods



    }