LongListSelector adjust based on screen width - xaml

Question

I am new to windows phone 8 development and i have a very basic question i believe.
I wish to make my LongListSelector have 100% width and height but all the things i have tried didnt work.
I have tried Auto, * etc but nothing seems to do it.
Here is my code:
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!--TitlePanel contains the name of the application and page title-->
<StackPanel Grid.Row="0" Margin="12,17,0,28">
<TextBlock Text="{Binding Path=LocalizedResources.ApplicationTitle, Source={StaticResource LocalizedStrings}}" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock TextWrapping="Wrap" Text="{Binding Path=LocalizedResources.SetupsPageTitle, Source={StaticResource LocalizedStrings}}" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<phone:LongListSelector HorizontalAlignment="Left" Width="400" Height="400"
VerticalAlignment="Top"
Name="lstSetups" ItemsSource="{Binding BusRouteSetups}"
SelectionChanged="lstSetups_SelectionChanged"
LayoutMode="List">
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical" Margin="0,10,0,10" Background="Coral">
<TextBlock TextWrapping="Wrap" Margin="5" FontWeight="Bold" Text="{Binding Details.Title}" />
<TextBlock TextWrapping="Wrap" Margin="5" Text="{Binding Details.Description}" />
</StackPanel>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</Grid>
</Grid>
Any help will be much appreciated.

Answer 1

Use HorizontalAlignment = Stretch (also Vertical), then Width and Height of LLS will be set to maximum space that is available to that Control:
<phone:LongListSelector HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
Name="lstSetups" ItemsSource="{Binding BusRouteSetups}"
SelectionChanged="lstSetups_SelectionChanged"
LayoutMode="List">
Note that it's maximum height will be determined by Grid (parent of Control). While you have set RowDefinition's Height to * - it means that it will use all the remaining height of the screen (remaining - some space is used by first row (set to auto) - StackPanel with title).

Answer 2

HorizontalAlignment="Left" Width="400" Height="400" VerticalAlignment="Top"
Just remove this part of your code and then the control should be sretched automatically.