Making GridView Visible

我试图在windows 10通用应用程序中创建一个简单的弹出窗口。我创建了一个GridView

<GridView x:Name="PopUp" HorizontalAlignment="Left" Height="453" Margin="10,99,0,0" VerticalAlignment="Top" Width="340" Visibility="Collapsed">
            <TextBox x:Name="Teacher" Height="29" TextWrapping="Wrap" Text="Teacher's name" Width="330"/>
            <TextBox x:Name="Room" Height="29" TextWrapping="Wrap" Text="Room" Width="330"/>
            <TextBox x:Name="Time" Height="29" TextWrapping="Wrap" Text="Time" Width="330"/>
            <TextBox x:Name="Subject" Height="29" TextWrapping="Wrap" Text="Subject" Width="330"/>
            <ComboBox x:Name="Day" HorizontalAlignment="Left" VerticalAlignment="Top" Width="330" />
            <AppBarButton Icon="Cancel"  Label="" Height="51" Margin="80,0,0,0"/>
            <AppBarButton Icon="Accept" Label="" Height="48" Margin="-40,-70,0,0" BorderThickness="0"/>
        </GridView>

我有按钮"添加"。我希望我的GridView在用户按下添加按钮时变得可见，而不是他在GridView中感觉字段，按下"Ok"，GridView再次变得不可见。我使用了buttonclick事件，但它不起作用:

private void AppBarButton_Click(object sender, RoutedEventArgs e)
        {
            Popup pop = new Popup();
            pop.Visibility = Visibility.Visible;
        }

也许有另一种方式来创建一个弹出(或者我不知道它是怎么叫的)菜单，因为我不想创建单独的页面添加数据。

    private void AppBarButton_Click(object sender, RoutedEventArgs e)
    {           
        PopUp.Visibility = Visibility.Visible;
    }