https://blog.csdn.net/weixin_33812433/article/details/85356220
private Dictionary allViews = new Dictionary(); //包含所有页面
allViews.Add("Page3", new Uri("myPage/Page3.xaml(页面地址)", UriKind.Relative));
mainFrame.Navigate(allViews["Page3"]);//Frame类的导航函数,参数时页面的Uri