private void btnSave_Click(object sender, EventArgs e)
        {
            if (filePath != "")
            {
                //check exists
                Note noteCheck = NoteController.getNote(filePath);
                noteCheck.note = txtNote.Text;

                List <Link> listLink = LinkController.getListLinks(filePath);

                if (listKind != null)
                {
                    for (int i = 0; i < listLink.Count; i++)
                    {
                        Link link = listLink[i];
                        LinkController.deleteLink(link);
                    }
                }

                for (int i = 0; i < lbChooseKind.Items.Count; i++)
                {
                    Link link = new Link();
                    link.kind = lbChooseKind.Items[i].ToString();
                    link.note = filePath;
                    LinkController.addLink(link);
                }

                NoteController.updateNote(noteCheck);
            }
        }