private void kháchHàngToolStripMenuItem_Click(object sender, EventArgs e)
 {
     frm_KhachHang kh = new frm_KhachHang();
     kh.ShowDialog();
 }
        private void kháchHàngToolStripMenuItem_Click(object sender, EventArgs e)
        {
            frm_KhachHang kh = new frm_KhachHang();

            kh.ShowDialog();
        }