void formLabelConfig_FormClosed(object sender, FormClosedEventArgs e)
{
formLabelConfig = null;
}
private void btnLabelConfig_Click(object sender, EventArgs e)
{
if (formLabelConfig == null)
{
formLabelConfig = new FormLabelConfig();
formLabelConfig.FormClosed += formLabelConfig_FormClosed;
formLabelConfig.MdiParent = this;
}
formLabelConfig.WindowState = FormWindowState.Maximized;
formLabelConfig.Show();
formLabelConfig.BringToFront();
}