ListBox scrolling with variable height - silverlight

Question

I have a problem with ListBox scrolling. Everytime I have more items than can be shown on screen and I try to scroll through the list it automatically snaps back to the top. I found this can be fixed by setting a fixed height to the ListBox.
However, I need to add items to the list dynamically and hence the height changes.
The Listbox is in the second row of a grid nested in a PivotItem.
How can I either set the height of the Listbox dynamically with XAML or achieve a scrolling effect that does not always snap to the top and hence prevents me from reading/editing items on the bottom?
Here is the XAML:
<Grid x:Name="LayoutRoot">
...
<controls:Pivot Title="Malts">
<controls:PivotItem Header="Gravity" Name="GravityPivot">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid> some more controls in row 0</Grid>
<Grid
Grid.Row="1">
<ListBox
VerticalAlignment="Stretch"
ItemsSource="{Binding ItemList}"
Padding="10,10,0,10"
ItemContainerStyle="{StaticResource ListBoxItemStyle}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock
Style="{StaticResource PhoneTextExtraLargeStyle}"
Text="{Binding Name}"
VerticalAlignment="Bottom"/>
<StackPanel>
<StackPanel
Orientation="Horizontal" >
<TextBlock
Text="{Binding Amount, Converter={StaticResource WeightConverter},StringFormat=' {0:f2}'}"
Margin="10,0,5,0"
Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock
Text="{Binding ., Converter={StaticResource UnitExtension}, ConverterParameter='Weight'}"
Style="{StaticResource PhoneTextNormalStyle}"/>
</StackPanel>
</StackPanel>
<toolkit:ContextMenuService.ContextMenu>
<toolkit:ContextMenu>
<toolkit:MenuItem
Header="Edit"
Command="{Binding ElementName=MaltList, Path=DataContext.EditCommand}"
CommandParameter="{Binding}"/>
<toolkit:MenuItem
Header="Remove"
Command="{Binding ElementName=MaltList, Path=DataContext.RemoveCommand}"
CommandParameter="{Binding}"/>
</toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Grid>
</controls:PivotItem>
Thank you!

Answer 1

Try this, should fix you up;
<ListBox>
<!-- You want this part... -->
<ListBox.Template>
<ControlTemplate>
<ScrollViewer HorizontalScrollBarVisibility="Auto"
VerticalScrollBarVisibility="Auto">
<ItemsPresenter/>
</ScrollViewer>
</ControlTemplate>
</ListBox.Template>
</ListBox>