private void btnDuan_Click(object sender, EventArgs e)
{
Quanlyduan frmda = new Quanlyduan();
frmda.Show();
this.Hide();
}
private void hopdongToolStripMenuItem_Click(object sender, EventArgs e)
{
Quanlyduan frmda = new Quanlyduan();
frmda.TopLevel = false;
pnlMain.Controls.Add(frmda);
frmda.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
frmda.Dock = DockStyle.Fill;
frmda.Show();
}