private void form01ToolStripMenuItem_Click(object sender, EventArgs e)
{
if (_form01 == null)
{
_form01 = new Form01(this);
_form01.MdiParent = this;
_form01.FormClosed += new FormClosedEventHandler(form01_FormClosed);
_form01.Show();
}
else
{
_form01.Activate();
}
}
void form01_FormClosed(object sender, FormClosedEventArgs e)
{
_form01 = null;
}