Silverlight Grid-伸展到父母的容器大小，但不扩展以容纳儿童

<ScrollViewer x:Name=\"LayoutRoot\" BorderThickness=\"0\" Padding=\"0\" ScrollViewer.HorizontalScrollBarVisibility=\"Auto\" ScrollViewer.VerticalScrollBarVisibility=\"Auto\">

    <Grid Background=\"White\">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height=\"Auto\"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Border Background=\"{StaticResource DefaultBackgroundBrush}\" BorderBrush=\"{StaticResource DefaultBorderBrush}\" BorderThickness=\"0,0,0,1\">
            <!--Some header content-->
        </Border>
        <sdk:Frame x:Name=\"Frame\" Grid.Row=\"1\" UriMapper=\"{StaticResource UriMapper}\" ContentLoader=\"{StaticResource ContentLoader}\" BorderThickness=\"0\" />
    </Grid>
</ScrollViewer>

<navigation:Page 
       xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\" 
       xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\" 
       xmlns:d=\"http://schemas.microsoft.com/expression/blend/2008\"
       xmlns:mc=\"http://schemas.openxmlformats.org/markup-compatibility/2006\"
       xmlns:navigation=\"clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation\" xmlns:sdk=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk\" x:Class=\"MyNamespace.MyPage\" mc:Ignorable=\"d\"
       d:DesignWidth=\"640\" d:DesignHeight=\"480\"
        Title=\"{StaticResource PageTitle}\">
<Grid x:Name=\"LayoutRoot\">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height=\"Auto\"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <StackPanel d:LayoutOverrides=\"Width\" Visibility=\"Collapsed\">
            <!-- Some header content -->
        </StackPanel>
        <Grid Grid.Row=\"1\">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height=\"Auto\"/>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <TextBlock TextWrapping=\"Wrap\" Text=\"Titletext\" FontSize=\"13.333\" FontWeight=\"Bold\" d:LayoutOverrides=\"Height\"/>
            <RichTextBox BorderThickness=\"0\" IsReadOnly=\"True\" Background=\"{x:Null}\" BorderBrush=\"{x:Null}\" VerticalScrollBarVisibility=\"Auto\" Grid.Row=\"1\" Padding=\"0\">
                <Paragraph><Run Text=\"Text that will force the grid to expand.\"/></Paragraph>
            </RichTextBox>
        </Grid>
    </Grid>
</Grid></navigation:Page>