XAML Grid layout - xaml

Question

I am developing a XAML based app and I have a spacing/layout issue. I currently have my main page as a 1 column grid. I have a ListBox though in which I need my data template to be displayed over 2 columns. The first data element should take up 75% of the screen and the second data element should take up the rest. When I run my app, the data from my listbox items are bunched on the left hand side of the screen. How can I change this behavior?
<Grid x:Name="LayoutRoot">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="2*"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="9*"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="12"/>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="12"/>
</Grid.ColumnDefinitions>
<!--My Section-->
<Grid Grid.Row="3" Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="Selected Location" FontWeight="Bold" Style="{StaticResource grayTextBox}"/>
<Line Grid.Row="1" Grid.Column="0" Stroke="White" StrokeThickness="1" />
<ListBox Grid.Row="2" ItemsSource="{Binding Path=SelectedLocations, Mode=TwoWay}" HorizontalContentAlignment="Stretch" Visibility="{Binding Path=IsSelectedLocationAvailable, Converter={StaticResource visibilityConverter}}">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid ShowGridLines="True">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="*" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=Name}" />
<TextBlock Grid.Row="1" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=Address}" />
<TextBlock Grid.Row="2" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=CityStateZip}" />
<StackPanel Grid.Row="0" Grid.Column="1" Grid.RowSpan="3" Orientation="Horizontal" HorizontalAlignment="Right">
<Rectangle Fill="Orange" />
<Rectangle Fill="Blue" />
</StackPanel>
</Grid>

Answer 1

Why use a Grid to center the content?
I currently have my main page as a 1 column grid
Why use a grid if it has just 1 column? Use margin on the stackpanel items.
<Grid x:Name="LayoutRoot">
<StackPanel Orientation="Vertical">
<TextBlock Text="Selected Location" FontWeight="Bold" Style="{StaticResource grayTextBox}"/>
<Line Stroke="White" StrokeThickness="1" />
<ListBox ItemsSource="{Binding Path=SelectedLocations, Mode=TwoWay}" HorizontalContentAlignment="Stretch" Visibility="{Binding Path=IsSelectedLocationAvailable, Converter={StaticResource visibilityConverter}}">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid ShowGridLines="True">
<Grid.RowDefinitions>
<RowDefinition Height="*" />
<RowDefinition Height="*" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=Name}" />
<TextBlock Grid.Row="1" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=Address}" />
<TextBlock Grid.Row="2" Grid.Column="0" Foreground="#ffb107" Text="{Binding Path=CityStateZip}" />
<StackPanel Grid.Row="0" Grid.Column="1" Grid.RowSpan="3" Orientation="Horizontal" HorizontalAlignment="Right">
<Rectangle Fill="Orange" />
<Rectangle Fill="Blue" />
</StackPanel>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</Grid>