AppBar : TopAppBar / BottomAppBar บน Windows Store Apps (C#)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using Windows.UI.Popups;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238

namespace WindowsStoreApps
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    /// 

    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
        }

        private void AppBarButton_Click(object sender, RoutedEventArgs e)
        {
            MessageDialog msgDialog = new MessageDialog("AppBar Clicked", "Hi");
            msgDialog.ShowAsync();

        }

        private void btnShow_Click(object sender, RoutedEventArgs e)
        {
            if (this.TopAppBar != null)
            {
                this.TopAppBar.IsOpen = true;
            }

            if (this.BottomAppBar != null)
            {
                this.BottomAppBar.IsOpen = true;
            }
        }

    }
}

    <Page.BottomAppBar>
        <CommandBar>
            <AppBarToggleButton Icon="Shuffle" Label="Shuffle" Click="AppBarButton_Click"/>
            <AppBarToggleButton Icon="RepeatAll" Label="Repeat" Click="AppBarButton_Click"/>
            <AppBarSeparator/>
            <AppBarButton Icon="Back" Label="Back" Click="AppBarButton_Click"/>
            <AppBarButton Icon="Stop" Label="Stop" Click="AppBarButton_Click"/>
            <AppBarButton Icon="Play" Label="Play" Click="AppBarButton_Click"/>
            <AppBarButton Icon="Forward" Label="Forward" Click="AppBarButton_Click"/>

            <CommandBar.SecondaryCommands>
                <AppBarButton Icon="Like" Label="Like" Click="AppBarButton_Click"/>
                <AppBarButton Icon="Dislike" Label="Dislike" Click="AppBarButton_Click"/>
            </CommandBar.SecondaryCommands>
        </CommandBar>
    </Page.BottomAppBar>