//新建
private void tsm_NewItem_Click(object sender, EventArgs e)
{
//实例化一个子窗体对象
FrmChild child = new FrmChild();
//设置窗体的父窗体
child.MdiParent = this;
child.Show();
}
//关闭
private void tsm_Close_Click(object sender, EventArgs e)
{
FrmChild frm = (this.ActiveMdiChild) as FrmChild;
frm.Close();
}