c# - 如何将按钮添加到 UIDocumentInteractionController 预览

Question

我UIDocumentInteractionController用于文件预览：

interactionController = UIDocumentInteractionController.FromUrl(url);    
interactionController.Delegate = new UIDocumentInteractionControllerDelegateClass(this);    
InvokeOnMainThread(delegate{interactionController.PresentPreview(true);}
});

如何在视图顶部添加自定义按钮以执行某些操作？