Xamarin PCL -如何向/从FTP服务器上传/下载文件？

using System;
using System.IO;
using System.Net;

public class FtpUploader
{
    public void UploadFile(string ftpServerUrl, string username, string password, string localFilePath, string remoteFilePath)
    {
        // 创建FTP请求对象
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(ftpServerUrl + "/" + remoteFilePath);
        request.Method = WebRequestMethods.Ftp.UploadFile;
        request.Credentials = new NetworkCredential(username, password);

        // 读取本地文件内容
        byte[] fileContents;
        using (StreamReader sourceStream = new StreamReader(localFilePath))
        {
            fileContents = Encoding.UTF8.GetBytes(sourceStream.ReadToEnd());
        }

        // 上传文件到FTP服务器
        using (Stream requestStream = request.GetRequestStream())
        {
            requestStream.Write(fileContents, 0, fileContents.Length);
        }

        // 获取FTP服务器的响应
        using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
        {
            Console.WriteLine("上传文件成功，服务器响应：{0}", response.StatusDescription);
        }
    }
}

using System;
using System.IO;
using System.Net;

public class FtpDownloader
{
    public void DownloadFile(string ftpServerUrl, string username, string password, string remoteFilePath, string localFilePath)
    {
        // 创建FTP请求对象
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(ftpServerUrl + "/" + remoteFilePath);
        request.Method = WebRequestMethods.Ftp.DownloadFile;
        request.Credentials = new NetworkCredential(username, password);

        // 获取FTP服务器的响应
        using (FtpWebResponse response = (FtpWebResponse)request.GetResponse())
        {
            // 读取FTP服务器返回的文件内容
            using (Stream responseStream = response.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(responseStream))
                {
                    string fileContents = reader.ReadToEnd();

                    // 将文件内容写入本地文件
                    using (StreamWriter writer = new StreamWriter(localFilePath))
                    {
                        writer.Write(fileContents);
                    }
                }
            }

            Console.WriteLine("下载文件成功，服务器响应：{0}", response.StatusDescription);
        }
    }
}