C#MID中同一个子窗体只能弹出一个

foreach (Form f in this.MdiChildren)
{
if (null != f &&f is yourFormName )
{
f.Activate();
return;
}
else
{
//如果要关闭非需要窗口，注释下面的语句
//f.Close();
}
}

yourFormName frm = new yourFormName();
frm.MdiParent = this;
frm.WindowState = FormWindowState.Maximized;
frm.Show();