private void btn_Submit_Click(object sender, EventArgs e)
{
// code xu ly them moi nha cung cap
ncc.Name = textBoxTenNCC.Text;
ncc.Address = textBoxDiaChi.Text;
ncc.Phone = textBoxSDT.Text;
ncc.Email = textBoxEmail.Text;
ctr.Insert(ncc);
// dong form
Close();
}