unnecessary spacing in windows phone keypad. Is this a OS bug?

Question

I came across a rather unusual effect in the windows phone keypad, in the portrait mode. I have a textbox at the bottom of my grid, and below it is the app bar. Now when the text box gains focus, There is an unnecessary spacing between the textbox and the keypad. I have pointed it out in this pic

.

Also here is my code,

   <Grid x:Name="LayoutRoot" Background="Green">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
        <TextBlock Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}" Margin="12,0"/>
        <TextBlock Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
    </StackPanel>

    <!--ContentPanel - place additional content here-->
    <Grid Background="PeachPuff" x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*" MaxHeight="100"/>
        </Grid.RowDefinitions>
        <ScrollViewer x:Name="scrollthis">
            <StackPanel x:Name="mystack"/>
        </ScrollViewer>
        <TextBox InputScope="Search" Grid.Row="1" x:Name="myTextBox"/>
    </Grid>

    <!--Uncomment to see an alignment grid to help ensure your controls are
        aligned on common boundaries.  The image has a top margin of -32px to
        account for the System Tray. Set this to 0 (or remove the margin altogether)
        if the System Tray is hidden.

        Before shipping remove this XAML and the image itself.-->
    <!--<Image Source="/Assets/AlignmentGrid.png" VerticalAlignment="Top" Height="800" Width="480" Margin="0,-32,0,0" Grid.Row="0" Grid.RowSpan="2" IsHitTestVisible="False" />-->
</Grid>
<phone:PhoneApplicationPage.ApplicationBar>
    <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True">
        <shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="enter text" Click="ApplicationBarIconButton_Click_1"/>
    </shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>

On app bar click I do the following.

    private void ApplicationBarIconButton_Click_1(object sender, EventArgs e)
    {
        TextBlock text = new TextBlock() { Text = myTextBox.Text, Margin = new Thickness(0,0,0,5) };
        myTextBox.Text = "";
        mystack.Children.Add(text);
    }

If this is an OS bug, should I look for a hack? Also please note that this spacing is not there in the landscape mode.

UPDATE

I just found out it happens only when there is an app bar at the bottom in the portrait mode.

UPDATE

I also noticed one more thing, initially even if I handle the grid margins, after entering some text, the spacing starts to grow.

Answer 1

This was a bug which got fixed in GDR 3 Update.