/// <summary> /// 先关后开. /// </summary> /// <param name="sender"></param> /// <param name="e"></param> private void closeOpenToolStripMenuItem_Click(object sender, EventArgs e) { // 遍历当前窗口的所有 mid 子窗口. foreach (Form oldForm in this.MdiChildren) { // 如果窗口类型为 指定类型,那么先关闭掉. if (oldForm is FormCloseOpen) { oldForm.Close(); } } // 关闭旧窗口以后,简单创建新窗口 并显示. FormCloseOpen newForm = new FormCloseOpen(); newForm.MdiParent = this; newForm.Show(); }