Free FTP Library

Why don't you use the libraries that come with the .NET framework: http://msdn.microsoft.com/en-us/library/ms229718.aspx?

EDIT: 2019 April by https://stackoverflow.com/users/1527/ This answer is no longer valid. Other answers are endorsed by Microsoft.

They were designed by Microsoft who no longer recommend that they should be used:

We don't recommend that you use the FtpWebRequest class for new development. For more information and alternatives to FtpWebRequest, see WebRequest shouldn't be used on GitHub. (https://docs.microsoft.com/en-us/dotnet/api/system.net.ftpwebrequest?view=netframework-4.7.2)

The 'WebRequest shouldn't be used' page in turn points to this question as the definitive list of libraries!

edtFTPnet is a free, fast, open source FTP library for .NET, written in C#.

After lots of investigation in the same issue I found this one to be extremely convenient: https://github.com/flagbug/FlagFtp

For example (try doing this with the standard .net "library" - it will be a real pain) -> Recursively retreving all files on the FTP server:

  public IEnumerable<FtpFileInfo> GetFiles(string server, string user, string password)
    {
        var credentials = new NetworkCredential(user, password);
        var baseUri = new Uri("ftp://" + server + "/");

        var files = new List<FtpFileInfo>();
        AddFilesFromSubdirectory(files, baseUri, credentials);

        return files;
    }

    private void AddFilesFromSubdirectory(List<FtpFileInfo> files, Uri uri, NetworkCredential credentials)
    {
        var client = new FtpClient(credentials);
        var lookedUpFiles = client.GetFiles(uri);
        files.AddRange(lookedUpFiles);

        foreach (var subDirectory in client.GetDirectories(uri))
        {
            AddFilesFromSubdirectory(files, subDirectory.Uri, credentials);
        }
    }