private void btn_xuatnhap_Click(object sender, EventArgs e)
{
this.Hide();
frmPhieuMuonTra muontra = new frmPhieuMuonTra();
muontra.ShowDialog();
}
private void quảnLýPhiếuMượnTrảToolStripMenuItem_Click(object sender, EventArgs e)
{
this.Hide();
frmPhieuMuonTra muontra = new frmPhieuMuonTra();
muontra.ShowDialog();
}