menuStrip之MdiWindowListItem判断子窗口是否被打开的方法

       /// <summary>
        /// 打开子菜单
        /// 可以判断是否被打开,已经被打开则激活
        /// </summary>
        /// <param name="childType">typeof(From)获取子菜单类型</param>
        private void OpenChildForm(Type childType)//传进子窗口的类型,如何获得类型呢?
        {
            bool isOpened = false;
            foreach (Form child in this.MdiChildren)
            {
                if (child.GetType() == childType)
                {
                    child.Activate();
                    isOpened = true;
                    break;
                }
            }
            if (!isOpened)
            {
                //动态创建form实例
                Form frm = (Form)Activator.CreateInstance(childType);
                frm.MdiParent = this;
                frm.WindowState = FormWindowState.Maximized;
                frm.Show();
            }
        }