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:\\test\download";

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:\testfile","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();
                }
            }
        }

如有疑问  可以往[e-mail]发邮件，我会第一时间给你解答的