private void IconsListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     //导航页面
     if (Translation.IsSelected)
     {
         MainWindowsFrame.Navigate(typeof(Translation));
     }
     if (Pronunciation.IsSelected)
     {
         MainWindowsFrame.Navigate(typeof(Pronunciation));
     }
     if (Instruction.IsSelected)
     {
         MainWindowsFrame.Navigate(typeof(Instruction));
     }
 }
 public MainPage()
 {
     this.InitializeComponent();
     IconsListBox.SelectedItem = Translation;
     MainWindowsFrame.Navigate(typeof(Translation));
 }