SFTP_Connect_And_Download_Sample.cs

private static void SFTP_Connect_And_Download_Sample()
{
    var host = "sftp_server_address.com";
    var port = 999;
    var username = "your_username";
    var passphrase = "your_passphrase";
    var privateKeyLocalFilePath = @"your_localpath\...\PrivateKeyOpenSSH.ppk";

    var remoteFolderPath = "/";
    var localFolferPath = @"D:\locafiles\";

    var key = File.ReadAllText(privateKeyLocalFilePath);
    var buf = new MemoryStream(Encoding.UTF8.GetBytes(key));
    var privateKeyFile = new PrivateKeyFile(buf, passphrase);
    var connectionInfo = new ConnectionInfo(host, port, username,
        new PrivateKeyAuthenticationMethod(username, privateKeyFile));
    using (var client = new SftpClient(connectionInfo))
    {
        client.Connect();
        var files = client.ListDirectory(remoteFolderPath);
        foreach (var file in files)
        {
            Console.WriteLine(file);
            using (var targetFile = new FileStream(Path.Combine(localFolferPath, file.Name), FileMode.Create))
            {
                client.DownloadFile(file.FullName, targetFile);
                targetFile.Close();
            }
        }
        client.Disconnect();
    }
}