解决点击MDI父窗体下拉菜单，子窗体重复出现的问题

private void 培训信息TToolStripMenuItem_Click(object sender, EventArgs e)

{

foreach (Form form in Application.OpenForms)

{

if (form.Name == "Zhuce_Train")//子窗体的Name属性

{

form.Activate();

return;

}

}

Zhuce_Train z = new Zhuce_Train();

z.MdiParent = this;

z.WindowState = FormWindowState.Maximized; //最大化运行

z.Show();

}