【FTP】C# System.Net.FtpClient库连接ftp服务器(下载文件)

如果自己单枪匹马写一个连接ftp服务器代码那是相当恐怖的（socket通信），有一个评价较高的dll库可以供我们使用。

那就是System.Net.FtpClient，链接地址：https://netftp.codeplex.com

然后下载该资源，我们就可以使用它的函数了。这里介绍一下如何使用System.Net.FtpClient链接ftp服务器并下载服务器中的文件。

千万别忘了添加引用——导入System.Net.FtpClient.dll.

还有就是 using System.Net.FtpClient;

            using System.Net;

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Net;
using System.Net.FtpClient;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace FTP_Client
{
public class FTPConnection
{

public FTPConnection() { }

/// <summary>
/// 连接FTP服务器函数
/// </summary>
/// <param name="strServer">服务器IP</param>
/// <param name="strUser">用户名</param>
/// <param name="strPassword">密码</param>
public bool FTPIsConnected(string strServer, string strUser, string strPassword)
{
using (FtpClient ftp = new FtpClient())
{
ftp.Host = strServer;
ftp.Credentials = new NetworkCredential(strUser, strPassword);
ftp.Connect();
return ftp.IsConnected;
}
}

/// <summary>
/// FTP下载文件
/// </summary>
/// <param name="strServer">服务器IP</param>
/// <param name="strUser">用户名</param>
/// <param name="strPassword">密码</param>
/// <param name="Serverpath">服务器路径，例子："/Serverpath/"</param>
/// <param name="localpath">本地保存路径</param>
/// <param name="filetype">所下载的文件类型,例子：".rte"</param>
public bool FTPIsdownload(string strServer, string strUser, string strPassword,string Serverpath, string localpath, string filetype)
{

FtpClient ftp = new FtpClient();
ftp.Host = strServer;
ftp.Credentials = new NetworkCredential(strUser, strPassword);
ftp.Connect();

string path = Serverpath;
string destinationDirectory = localpath;
List<string> documentname = new List<string>();
bool DownloadStatus = false;

if (Directory.Exists(destinationDirectory))
{
#region  从FTP服务器下载文件
foreach (var ftpListItem in ftp.GetListing(path, FtpListOption.Modify | FtpListOption.Size)
.Where(ftpListItem => string.Equals(Path.GetExtension(ftpListItem.Name), filetype)))
{
string destinationPath = string.Format(@"{0}\{1}", destinationDirectory, ftpListItem.Name);
using (Stream ftpStream = ftp.OpenRead(ftpListItem.FullName))
using (FileStream fileStream = File.Create(destinationPath, (int)ftpStream.Length))
{
var buffer = new byte[200 * 1024];
int count;
while ((count = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
{
fileStream.Write(buffer, 0, count);
}
}
documentname.Add(ftpListItem.Name);
}
#endregion

#region  验证本地是否有该文件
string[] files = Directory.GetFiles(localpath, "*"+filetype);
int filenumber = 0;
foreach(string strfilename in files)
{
foreach(string strrecievefile in documentname)
{
if (strrecievefile == Path.GetFileName(strfilename))
{
filenumber++;
break;
}
}
}
if(filenumber==documentname.Count)
{
DownloadStatus = true;
}
#endregion
}
return DownloadStatus;
}

}
}

 注意：如果存放在服务器的文件是放在根目录下，那么服务器路径只需填写“/”，即可。