private void frmtinhtrang_Load(object sender, EventArgs e)
{
DAO.connect();
hienthi();
}
private void frmchitietthuesach_Load(object sender, EventArgs e)
{
DAO.connect();
loaddata();
}
private void frmthuesach_Load(object sender, EventArgs e)
{
DAO.connect();
ketnoi();
}