如果是我，我会创建一个SDI应用程序，实现所有的可切换的表单作为用户控件，并将它们放在主窗口上。此时，我将使用菜单显示/隐藏相应的表单。

If it were me, I would create a SDI application, implement all of the switchable forms as user controls, and place them on the main window. At that point, I would use the menu to show/hide the appropriate forms.