private void barButtonItem_ThoiHan_ItemClick(object sender, ItemClickEventArgs e)
{
if (formThoiHanSuDung == null)
{
formThoiHanSuDung = new F_Main_ThoiHanSuDung();
formThoiHanSuDung.MdiParent = this;
formThoiHanSuDung.FormClosed += new FormClosedEventHandler(formThoiHanSuDung_FormClosed);
formThoiHanSuDung.Show();
}
else
{
formThoiHanSuDung.Activate();
}
}
void formThoiHanSuDung_FormClosed(object sender, FormClosedEventArgs e)
{
formThoiHanSuDung = null;
}