private void btnKhach_Click(object sender, EventArgs e)
{
this.Hide();
KHACH khach = new KHACH();
khach.ShowDialog();
this.Close();
}
private void button3_Click(object sender, EventArgs e)
{
this.Hide();
KHACH dshd = new KHACH();
dshd.ShowDialog();
this.Close();
}