C# Ftp方式下载文件（无用户认证方式,支持断点续传）

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.IO;

namespace ConsoleTest
{
class FtpDlder
{
public void download(String url, String localFile)
{
FtpWebRequest remoteFileLenReq; // 此请求是为了获取远程文件长度
FtpWebRequest remoteFileReadReq;// 此请求是为了读取文件
Stream readStream = null;       // 读取流
FileStream writeStream = null;  // 写本地文件流

try
{
writeStream = new FileStream(localFile, FileMode.Append);
long startPosition=writeStream.Length;// 读出本地文件已有长度

// 下面代码目的是取远程文件长度
remoteFileLenReq = (FtpWebRequest)FtpWebRequest.Create(url);
remoteFileLenReq.UseBinary = true;
remoteFileLenReq.ContentOffset = 0;
remoteFileLenReq.Method = WebRequestMethods.Ftp.GetFileSize;
FtpWebResponse rsp = (FtpWebResponse)remoteFileLenReq.GetResponse();
long totalByte = rsp.ContentLength;
rsp.Close();

if (startPosition >= totalByte)
{
System.Console.WriteLine("本地文件长度" + startPosition + "已经大于等于远程文件长度" + totalByte);
writeStream.Close();

return;
}

// 初始化读取远程文件请求
remoteFileReadReq = (FtpWebRequest)FtpWebRequest.Create(url);
remoteFileReadReq.UseBinary = true;
remoteFileReadReq.KeepAlive = false;
remoteFileReadReq.ContentOffset = startPosition;
remoteFileReadReq.Method = WebRequestMethods.Ftp.DownloadFile;
FtpWebResponse response = (FtpWebResponse)remoteFileReadReq.GetResponse();
readStream = response.GetResponseStream();

long downloadedByte = startPosition;
int bufferSize = 512;
byte[] btArray = new byte[bufferSize];
int contentSize = readStream.Read(btArray, 0, btArray.Length);

while (contentSize > 0)
{
downloadedByte += contentSize;
int percent = (int)(downloadedByte * 100 / totalByte);
System.Console.WriteLine("percent=" + percent + "%");

writeStream.Write(btArray, 0, contentSize);
contentSize = readStream.Read(btArray, 0, btArray.Length);
}
readStream.Close();
writeStream.Close();
response.Close();
return;
}
catch (Exception)
{
return;

}
finally
{
if (readStream != null)
{
readStream.Close();
}
if (writeStream != null)
{
writeStream.Close();
}
}
}
}
}

static void Main(string[] args)
{
// Ftp下载测试，无用户身份测试
FtpDlder fd = new FtpDlder();
fd.download("ftp://192.168.0.109/jump.jpg", "c:\\asd\\jump.jpg");
}