C#本地文件下载以及FTP文件服务下载（以Pdf文件为例）

一、C#实现本地文件下载

1、文件下载的路径  文件名称 以及文件下载之后要放的位置  这三个变量是必须要的

2、定义以下四个对象：    

FileWebRequest ftpWebRequest = null;
FileWebResponse ftpWebResponse = null;
Stream ftpResponseStream = null;
FileStream outputStream = null;

3、创建文件下载存放位置的路径（不需要手动创建，如果路径存在就创建 不存在就不创建）

      Directory.CreateDirectory(LocalFolder);//创建文件夹名称

     * 这里提一点  Path.Combine（）这个就是文件路径拼接的函数，会自动判断，在需要的文件加  \  

    比如 string filePath=  Path.Combine（“D:”，“test”,"download"）;  //  filePath="D:\testdownload";

4、  然后执行以下代码  即可完成文件下载   

      ftpWebRequest = (FileWebRequest)FileWebRequest.Create(new Uri(uri));
            ftpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile;
            ftpWebResponse = (FileWebResponse)ftpWebRequest.GetResponse();
            ftpResponseStream = ftpWebResponse.GetResponseStream();
            long contentLength = ftpWebResponse.ContentLength;
            int bufferSize = 2048;
            byte[] buffer = new byte[bufferSize];
            int readCount;
            readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
            while (readCount > 0)
            {
                outputStream.Write(buffer, 0, readCount);
                readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
            }

5、代码写完之后要思考，下载文件的时候如何出现异常  这时在整个代码加个 Try{} catch{}

具体代码如下：  

 public static void Main(string[] args)
        {
            TestFile tf = new TestFile();
            tf.fileDownload("D:/testFile/", "下载ftp文件.txt", "C:/Users/17/Desktop/文件", "下载ftp文件.txt", DateTime.Now.ToShortDateString());
        }

      /// <summary>
        /// 下载文件
        /// </summary>
        /// <param name="localPath">本地文件地址(没有文件名)</param>
        /// <param name="localFileName">本地文件名</param>
        /// <param name="ftpPath">下载的ftp的路径</param>
        /// <param name="ftpFileName">下载的ftp的文件名</param>
        public bool fileDownload(string localPath, string localFileName, string ftpPath, string ftpFileName, string date)
        {
            bool success = false;
            //FtpWebResponse ftpWebResponse = null;
            FileWebRequest ftpWebRequest = null;
            FileWebResponse ftpWebResponse = null;
            Stream ftpResponseStream = null;
            FileStream outputStream = null;
            try
            {
                //string date = DateTime.Now.ToShortDateString().ToString();//获取系统时间
                string date1 = date.Replace("/", "");//winods 中文件命名不能有 /   去掉指定字符串 /
                //localPath = localPath + date1 + "/";//拼接路径

                localPath=Path.Combine(localPath,date1)
                Directory.CreateDirectory(localPath);//创建文件夹名称
                outputStream = new FileStream(localPath + localFileName, FileMode.Create);//创建文件
                string uri = ftpRootURL + ftpPath + "/" + ftpFileName;//拼接目标文件路径

                string uri= Path.Combine(ftpRootURL,ftpPath,ftpFileName);
                ftpWebRequest = (FileWebRequest)FileWebRequest.Create(new Uri(uri));              
                //ftpWebRequest1.UseBinary = true;
                ftpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile;
                ftpWebResponse = (FileWebResponse)ftpWebRequest.GetResponse();
                ftpResponseStream = ftpWebResponse.GetResponseStream();
                long contentLength = ftpWebResponse.ContentLength;
                int bufferSize = 2048;
                byte[] buffer = new byte[bufferSize];
                int readCount;
                readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                }
                success = true;
            }
            catch (Exception e)
            {

                DirectoryInfo folder = new DirectoryInfo(localPath);
                StreamWriter log = new StreamWriter(localPath + "/" + DateTime.Now.ToShortDateString().ToString().Replace("/", "") + ".txt", true);
                log.WriteLine("发生异常时间:" + System.DateTime.Now.ToShortTimeString().ToString());
                log.WriteLine("发生异常信息:" + e.Message);
                log.WriteLine("发送异常对象:" + e.Source);
                log.WriteLine("调用堆栈:" + e.StackTrace.Trim());
                log.WriteLine("触动方法:" + e.TargetSite);
                log.WriteLine("   " + e.HResult);
                log.WriteLine("数据对象" + e.Data);
                log.WriteLine("____________________________________________________________");
                log.WriteLine();
                log.Close();
                success = false;
            }
            finally
            {
                if (outputStream != null)
                {
                    outputStream.Close();
                }
                if (ftpResponseStream != null)
                {
                    ftpResponseStream.Close();
                }

                if (ftpWebResponse != null)
                {
                    ftpWebResponse.Close();
                }
            }
            return success;
        }

二、 FTP 服务文件下载

这个功能其实和本地文件下载一样，只需要加几点即可 

1、FTP服务的地址；

具体代码如下

       private string ftpIP = "**********";

2、FTP文件服务的登录账号以及密码

具体代码如下      

private string ftpName = "*********";
private string ftpPassword = "******";
private string ftpRootURL = string.Empty;
FtpWebRequest reqFTP;

 3、获取FTP服务上的文件名称、FTP文件服务需要下载之后存放的路径以及下载功能的实现

FtpWebRequest ftpWebRequest = null;
            FtpWebResponse ftpWebResponse = null;
            Stream ftpResponseStream = null;
            FileStream outputStream = null;
            try
            {
                localFilePath = Path.Combine(localFilePath, ftpFileNameTime);
                Directory.CreateDirectory(localFilePath);//创建文件夹名称
                outputStream = new FileStream(Path.Combine(localFilePath, fileName), FileMode.Create);
                string uri = Path.Combine(ftpRootURL, ftpIP, fileName);
                ftpWebRequest = (FtpWebRequest)FileWebRequest.Create(new Uri(uri));
                ftpWebRequest.Credentials = new NetworkCredential(ftpName, ftpPassword);//登录ftp
                ftpWebRequest.UseBinary = true;
                ftpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile;
                ftpWebResponse = (FtpWebResponse)ftpWebRequest.GetResponse();
                ftpResponseStream = ftpWebResponse.GetResponseStream();
                long contentLength = ftpWebResponse.ContentLength;
                int bufferSize = 2048;
                byte[] buffer = new byte[bufferSize];
                int readCount;
                readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                }
            }
            catch (Exception ex)
            {

                MessageBox.Show(ex.Message）
                /*MessageBox.Show(ex.Message + "是否下载日志文件", "发送错误！", MessageBoxButtons.OKCancel);
                //点击确定  就执行下载日志文件，不然就不执行
                if (dr == DialogResult.OK)
                {
                    WriteLog log = new WriteLog();
                    log.Write_log(ex.Message);
                }*/
            }
            finally
            {
                if (outputStream != null)
                {
                    outputStream.Close();
                }
                if (ftpResponseStream != null)
                {
                    ftpResponseStream.Close();
                }

                if (ftpWebResponse != null)
                {
                    ftpWebResponse.Close();
                }
            }

5、具体代码如下：

namespace FtpDownLoad
{
    public class ftpFileDownload
    {

        private string ftpIP = "*************";
        private string ftpName = "2*******";
        private string ftpPassword = "*********";
        private string ftpRootURL = string.Empty;
        FtpWebRequest reqFTP;

      public static void Main(string[] args)
        {

                 ftpFileDownload ftpDown = new ftpFileDownload();
                 ftpDown.GetFileList("D:	estFile","37.pdt","20190703");

       }

        /// <summary>
        /// 文件下载
        /// </summary>
        /// <param name="localFilePath">下载路径</param>
        /// <param name="fileName">下载的名称</param>
        /// <param name="ftpFilePath">FTP路径</param>
        /// <param name="ftpFileNameTime">FTP文件的修改时间</param>

     public void FtpDownLoadFile(string localFilePath, string fileName, string ftpFileNameTime)
        {
            FtpWebRequest ftpWebRequest = null;
            FtpWebResponse ftpWebResponse = null;
            Stream ftpResponseStream = null;
            FileStream outputStream = null;
            try
            {
                localFilePath = Path.Combine(localFilePath, ftpFileNameTime);
                Directory.CreateDirectory(localFilePath);//创建文件夹名称
                outputStream = new FileStream(Path.Combine(localFilePath, fileName), FileMode.Create);
                string uri = Path.Combine(ftpRootURL, ftpIP, fileName);
                ftpWebRequest = (FtpWebRequest)FileWebRequest.Create(new Uri(uri));
                ftpWebRequest.Credentials = new NetworkCredential(ftpName, ftpPassword);//登录ftp
                ftpWebRequest.UseBinary = true;
                ftpWebRequest.Method = WebRequestMethods.Ftp.DownloadFile;
                ftpWebResponse = (FtpWebResponse)ftpWebRequest.GetResponse();
                ftpResponseStream = ftpWebResponse.GetResponseStream();
                long contentLength = ftpWebResponse.ContentLength;
                int bufferSize = 2048;
                byte[] buffer = new byte[bufferSize];
                int readCount;
                readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpResponseStream.Read(buffer, 0, bufferSize);
                }
            }
            catch (Exception ex)
            {

               MessageBox.Show(ex.Message);
              /*  DialogResult dr = MessageBox.Show(ex.Message + "是否下载日志文件", "发送错误！", MessageBoxButtons.OKCancel);
                //点击确定  就执行下载日志文件，不然就不执行
                if (dr == DialogResult.OK)
                {
                    WriteLog log = new WriteLog();
                    log.Write_log(ex.Message);
                }*/
            }
            finally
            {
                if (outputStream != null)
                {
                    outputStream.Close();
                }
                if (ftpResponseStream != null)
                {
                    ftpResponseStream.Close();
                }

                if (ftpWebResponse != null)
                {
                    ftpWebResponse.Close();
                }
            }
        }

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