Something

                fcw = new Gtk.FileChooserWidget(((Gtk.FileChooserAction)(0)));
                fcw.Name = "filechooserwidget1";
                fcw.SelectMultiple = false;
                fcw.ShowHidden = false;
                fcw.PreviewWidgetActive = false;
                fcw.FileActivated += clicked_file;

                Gtk.FileFilter dbfilter = new Gtk.FileFilter();
                dbfilter.Name = "MSDB Files";
                dbfilter.AddMimeType("application/x-sqlite3");
                dbfilter.AddPattern("*.db");

                fcw.AddFilter (dbfilter);

                window.Add (fcw);

                window.ShowAll ();

                Application.Run ();

        }

        static void delete_event (object obj, DeleteEventArgs args)

        {

                Application.Quit ();

        }

        static void clicked_file (object sender, System.EventArgs e)

        {

                string openFileName = "MILES";

                Console.WriteLine (openFileName);

        }

}