private void lịchSửHóaĐơnToolStripMenuItem_Click(object sender, EventArgs e)
{
fBillHistory f = new fBillHistory();
this.Hide();
f.ShowDialog();
this.Show();
}
private void lBillHistory_Click(object sender, EventArgs e)
{
fBillHistory f = new fBillHistory();
this.Hide();
f.ShowDialog();
this.Show();
}