private void mnuHoaDonBan_Click(object sender, EventArgs e)
{
frmHoaDonBan frm = new frmHoaDonBan();
frm.MdiParent = this;
frm.Show();
}
private void dgvTKHoaDon_CellClick(object sender, DataGridViewCellEventArgs e)
{
string mahd;
mahd = dgvTKHoaDon.CurrentRow.Cells["MaHDBan"].Value.ToString();
frmHoaDonBan frm = new frmHoaDonBan();
frm.txtMaHDBan.Text = mahd;
frm.StartPosition = FormStartPosition.CenterParent;
frm.ShowDialog();
}