如何多次推送同一个视图控制器实例

Question

public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        var scheduleButtoncontroller = (IntroController)Storyboard.InstantiateViewController("IntroController");
        var PriceButtonController = (PriceViewController)Storyboard.InstantiateViewController("PriceViewController");


        ScheduleButton.TouchUpInside += (o, e) =>
        {
            if (NavController.TopViewController as IntroController == null)
                this.NavController.PushViewController(scheduleButtoncontroller, true);
            SidebarController.CloseMenu();

        };

        PriceButton.TouchUpInside += (o, e) =>
        {
            if (NavController.TopViewController as PriceViewController == null)
                this.NavController.PushViewController(PriceButtonController, true);
            SidebarController.CloseMenu();

        };

我用它来按下幻灯片菜单上的按钮来推动视图控制器。当我导航到同一个视图两次时（例如我按下价格按钮并转到该屏幕，然后按下计划按钮导航到另一个屏幕，然后我再次按下价格按钮，它得到一个错误），我得到例外

抛出Objective-C异常。名称：NSInvalidArgumentException原因：不支持多次推送同一个视图控制器实例

如何解决此问题？