折叠和展开SplitContainer面板

在我的winform应用程序中有3个分割容器。splitContainer1, splitContainer2, splitContainer3

splitContainer1是主拆分容器。在它的panel1我把splitContainer2在它的panel2我有splitContainer3

然后我添加了两个按钮来折叠/隐藏splitContainer3面板:每当我点击一个按钮，它被折叠，但当我想要2个面板被折叠时，其中一个自动得到再次展开问题是什么?

private void btToggleCI_Click(object sender, EventArgs e)
{
    switch (splitContainer3.Panel1Collapsed)
    {
        case false:
            splitContainer3.Panel1Collapsed = true;
            btToggleCI.ForeColor = Color.Gray;
            break;
        case true:
            splitContainer3.Panel1Collapsed = false;
            btToggleCI.ForeColor = Color.Black;
            break;
    }
}
private void btToggleTestPlan_Click(object sender, EventArgs e)
{
    switch (splitContainer3.Panel2Collapsed)
    {
        case false:
            splitContainer3.Panel2Collapsed = true;
            btToggleTestPlan.ForeColor = Color.Gray;
            break;
        case true:
            splitContainer3.Panel2Collapsed = false;
            btToggleTestPlan.ForeColor = Color.Black;
            break;
    }
}