private void sINHVIÊNToolStripMenuItem_Click(object sender, EventArgs e)
{
if (sv == null)
{
sv = new Student_Form();
sv.FormClosed += new FormClosedEventHandler(SinhVien_Form_FormClosed);
sv.MdiParent = this;
sv.Show();
}
else
{
sv.Activate();
}
}
private void SinhVien_Form_FormClosed(object sender, FormClosedEventArgs e)
{
sv = null;
}