在C＃中，可以使用FtpWebRequest類來進行FTP文件上傳和下載。以下是一個簡單的例子：

文件上傳：

string ftpServerIP = "ftp://ftp.example.com/";
string ftpUsername = "username";
string ftpPassword = "password";

string filePath = "localfile.txt";
string ftpPath = "remotefile.txt";

FtpWebRequest request = (FtpWebRequest)WebRequest.Create(ftpServerIP + ftpPath);
request.Method = WebRequestMethods.Ftp.UploadFile;
request.Credentials = new NetworkCredential(ftpUsername, ftpPassword);

using (FileStream fileStream = File.OpenRead(filePath))
using (Stream ftpStream = request.GetRequestStream())
{
    fileStream.CopyTo(ftpStream);
}

文件下載：

string ftpServerIP = "ftp://ftp.example.com/";
string ftpUsername = "username";
string ftpPassword = "password";

string ftpPath = "remotefile.txt";
string filePath = "localfile.txt";

FtpWebRequest request = (FtpWebRequest)WebRequest.Create(ftpServerIP + ftpPath);
request.Method = WebRequestMethods.Ftp.DownloadFile;
request.Credentials = new NetworkCredential(ftpUsername, ftpPassword);

using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
using (Stream ftpStream = response.GetResponseStream())
using (FileStream fileStream = File.Create(filePath))
{
    ftpStream.CopyTo(fileStream);
}

請注意，這些代碼示例中的FTP服務器的URL、用戶名和密碼應更改為實際的值。