Wikipedia
EdtFTPnet
edtFTPnet is an open source FTP client library for Windows licensed under the LGPL. It was first released in 2003, and was ported from edtFTPj. It is supplied as a DLL and can be incorporated into Windows applications that require FTP functionality.
edtFTPnet has also been successfully tested for use on Mono, and so can be used on Unix platforms that support Mono.