PWAPP/PWAppUpdater/FTP/FTPManager.cs

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


namespace PWAppUpdater.FTP
{
    class FTPManager
    {
        private string BaseUri;
        private NetworkCredential credential;

        public FTPManager(string baseUri, string username, string password)
        {
            BaseUri = baseUri;
            credential = new NetworkCredential(username, password);
        }

        public void DownloadFile(string FTPPath, string localPath)
        {
            try
            {
                FtpWebRequest request = (FtpWebRequest)WebRequest.Create(BaseUri + FTPPath);
                request.Method = WebRequestMethods.Ftp.DownloadFile;
                request.Credentials = credential;
                request.KeepAlive = false;
                request.UseBinary = true;
                request.UsePassive = true;

                FtpWebResponse response = (FtpWebResponse)request.GetResponse();
                Stream responseStream = response.GetResponseStream();

                using (Stream s = File.Create(localPath))
                {
                    responseStream.CopyTo(s);
                }
                response.Close();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message.ToString());
            }
        }
    }
}