Windows 8 XAML Layout Issues - anchor control on right side of screen - xaml

Question

I'm struggling to understand how the xaml controls can help me accomplish the following layout:
I have a 3-column layout. The leftmost and center columns have listviews. The rightmost column simply has a clickable (tappable) stackpanel that navigates elsewhere. I want this stackpanel to be anchored to the right side of the page, halfway down (i.e. in CSS I would say right: 0, top: 50%).
My XAML is below. My strategy has been to create a horizontal parent stackpanel containing all 3 columns, and a vertical stackpanel with a textblock on top of a listview control in the leftmost and middle columns. However, the third stackpanel behaves in some unexpected ways:
It does not fill the horizontal space remaining to the right of the second stack panel. It seems to prefer to only take up the space required by whatever its child controls require. This means that I have to assign static values to child elements to try to line the clickable control up with the right side of the page. This means that when screen resolutions are different than what I'm designing for, this clickable control will be either off the right side of the page, or toward the middle of the page.
I can't coerce the clickable element in the third column (stackpanel, or any other control I try to use) to move halfway down the page. As I mentioned above, I want it to be halfway down the page, but it stubbornly sits at the top of its containing stackpanel.
I've looked at the canvas control, but don't want this to be static - this is so easy in CSS, I'm not sure why it's so complicated in XAML.
<!--
This grid acts as a root panel for the page that defines two rows:
* Row 0 contains the back button and page title
* Row 1 contains the rest of the page layout
-->
<Grid Style="{StaticResource LayoutRootStyle}">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1160"/>
<ColumnDefinition Width="206"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="140"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!-- Back button and page title -->
<Grid Grid.ColumnSpan="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Button x:Name="backButton" Click="GoBack" IsEnabled="{Binding Frame.CanGoBack, ElementName=pageRoot}" Style="{StaticResource BackButtonStyle}"/>
<TextBlock x:Name="pageTitle" Grid.Column="1" Text="{StaticResource AppName}" Style="{StaticResource PageHeaderTextStyle}"/>
</Grid>
<StackPanel Orientation="Horizontal" Grid.Row="1" HorizontalAlignment="Stretch" Grid.ColumnSpan="2">
<StackPanel
Orientation="Vertical"
Margin="0,0,40,0">
<StackPanel
Height="100"
Width="400"
HorizontalAlignment="Left"
Margin="40,15,0,0">
<StackPanel.Background>
<SolidColorBrush>
<Color>#FFFFFF</Color>
</SolidColorBrush>
</StackPanel.Background>
<TextBlock
Text="Announcements"
FontSize="42"
FontWeight="Light"
TextAlignment="Left"
Padding="0,25,25,25">
</TextBlock>
</StackPanel>
<ListView
HorizontalAlignment="Left"
Height="475"
Margin="40,15,0,0"
VerticalAlignment="Top"
Width="400"
ItemsSource="{Binding Incidents}"
IsItemClickEnabled="True"
SelectionMode="None"
ItemTemplate="{StaticResource Standard130ItemTemplate}"
ItemClick="Item_Click" >
</ListView>
</StackPanel>
<StackPanel
Orientation="Vertical"
Margin="40,0,0,0">
<StackPanel
Height="100"
Width="600"
HorizontalAlignment="Right"
Margin="0,15,40,0">
<StackPanel.Background>
<SolidColorBrush>
<Color>#FFFFFF</Color>
</SolidColorBrush>
</StackPanel.Background>
<TextBlock
Text="News from Yammer"
FontSize="42"
FontWeight="Light"
TextAlignment="Left"
Padding="0,25,25,25">
</TextBlock>
</StackPanel>
<ListView
HorizontalAlignment="Left"
Height="475"
Margin="40,15,0,0"
VerticalAlignment="Top"
Width="Auto"
ItemsSource="{Binding Incidents}"
IsItemClickEnabled="True"
SelectionMode="None"
ItemTemplate="{StaticResource Standard130ItemTemplate}"
ItemClick="Item_Click" >
</ListView>
</StackPanel>
<StackPanel Background="AliceBlue" Width="206" Height="628">
<TextBlock x:Name="stackPanel" Background="Black" Height="50" Width="20" HorizontalAlignment="Right" Margin="10,100,10,0" Opacity="0"/>
</StackPanel>
</StackPanel>

Answer 1

StackPanels only give enough space to their child elements as the need. I would recommend the following:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="2" HorizontalAlignment="Stretch" VerticalAlignment="Center">
<!-- Right most column -->
</StackPanel>
</Grid>
This was the stack panel stretches to fit the column.