private void tESTToolStripMenuItem2_Click(object sender, EventArgs e)
{
if (tbs == null)
{
tbs = new TestBills();
tbs.MdiParent = this;
tbs.FormClosed += new FormClosedEventHandler(tbs_FormClosed);
tbs.Show();
}
else
tbs.Activate();
}
private void tbs_FormClosed(object sender, FormClosedEventArgs e)
{
tbs = null;
// throw new NotImplementedException();
}