FTP文件操作之下載文件

前面寫了采用ftp上傳文件，有了上傳怎麼能夠沒有下載呢？如果只有上傳沒有下載，那上傳了也沒啥用了。所以今天就跟大家一起學習學習使用ftp下載文件。

知道了怎麼上傳，那麼下載也就變得很簡單了，上傳是把文件放到服務器，而下載是把文件從服務器取過來。一個是從本地讀文件，然後寫到服務器；另一個是從服務器讀文件，然後寫到本地。基本原理就是這樣，下面我們看看具體的代碼：

[csharp] 
/// <summary>  
/// FTP下載文件  
/// </summary>  
/// <param name="userId">ftp用戶名</param>  
/// <param name="pwd">ftp密碼</param>  
/// <param name="ftpPath">ftp文件路徑</param>  
/// <param name="filePath">下載保存路徑</param>  
/// <param name="fileName">ftp文件名</param>  
/// <returns></returns>  
public string  Download(string userId, string pwd, string ftpPath, string filePath, string fileName) 
{ 
    string sRet = "下載成功！";   
    FtpWebRequest reqFTP; 
    try 
    { 
        FileStream outputStream = new FileStream(filePath + fileName, FileMode.Create); 
 
        // 根據uri創建FtpWebRequest對象     
        reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(ftpPath + fileName)); 
 
        // 指定執行什麼命令    
        reqFTP.Method = WebRequestMethods.Ftp.DownloadFile; 
 
        // 指定數據傳輸類型    
        reqFTP.UseBinary = true; 
        reqFTP.UsePassive = false; 
 
        // ftp用戶名和密碼    
        reqFTP.Credentials = new NetworkCredential(userId, pwd); 
         
        FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse(); 
 
        // 把下載的文件寫入流  
        Stream ftpStream = response.GetResponseStream(); 
 
        long cl = response.ContentLength; 
 
        // 緩沖大小設置為2kb    
        int bufferSize = 2048; 
        int readCount; 
        byte[] buffer = new byte[bufferSize]; 
 
        // 每次讀文件流的2kb    
        readCount = ftpStream.Read(buffer, 0, bufferSize); 
        while (readCount > 0) 
        { 
            // 把內容從文件流寫入     
            outputStream.Write(buffer, 0, readCount); 
            readCount = ftpStream.Read(buffer, 0, bufferSize); 
        } 
 
        //關閉兩個流和ftp連接  
        ftpStream.Close(); 
        outputStream.Close(); 
        response.Close(); 
 
 
    } 
    catch (Exception ex) 
    { 
        sRet=ex.Message; 
    } 
 
    //返回下載結果（是否下載成功）  
    return sRet; 
}   

        /// <summary>
        /// FTP下載文件
        /// </summary>
        /// <param name="userId">ftp用戶名</param>
        /// <param name="pwd">ftp密碼</param>
        /// <param name="ftpPath">ftp文件路徑</param>
        /// <param name="filePath">下載保存路徑</param>
        /// <param name="fileName">ftp文件名</param>
        /// <returns></returns>
        public string  Download(string userId, string pwd, string ftpPath, string filePath, string fileName)
        {
            string sRet = "下載成功！"; 
            FtpWebRequest reqFTP;
            try
            {
                FileStream outputStream = new FileStream(filePath + fileName, FileMode.Create);

                // 根據uri創建FtpWebRequest對象  
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(ftpPath + fileName));

                // 指定執行什麼命令 
                reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;

                // 指定數據傳輸類型 
                reqFTP.UseBinary = true;
                reqFTP.UsePassive = false;

                // ftp用戶名和密碼 
                reqFTP.Credentials = new NetworkCredential(userId, pwd);
               
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();

                // 把下載的文件寫入流
                Stream ftpStream = response.GetResponseStream();

                long cl = response.ContentLength;

                // 緩沖大小設置為2kb 
                int bufferSize = 2048;
                int readCount;
                byte[] buffer = new byte[bufferSize];

                // 每次讀文件流的2kb 
                readCount = ftpStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    // 把內容從文件流寫入  
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpStream.Read(buffer, 0, bufferSize);
                }

                //關閉兩個流和ftp連接
                ftpStream.Close();
                outputStream.Close();
                response.Close();

            }
            catch (Exception ex)
            {
                sRet=ex.Message;
            }

            //返回下載結果（是否下載成功）
            return sRet;
        } 
以上代碼可以實現一個簡單的ftp下載的功能，只要在需要的地方調用此方法即可。代碼很簡單，功能很實用。

還有很多FTP的相關操作，以後會陸續跟大家分享，敬請期待！