ItemsControl, VirtualizingStackPanel and ScrollViewer height - wpf

Question

I want to display a important list of items using an ItemsControl.
The reason why I'm using an ItemsControl is that the DataTemplate is much more complex in the application I'm working on: The sample code provided only reflects the sizing problem I have.
I would like :
the ItemsControl to be virtualized because there is many items to display
its size to expand to its parent container automatically (the Grid)
<Grid>
<ItemsControl x:Name="My" ItemsSource="{Binding Path=Names}">
<ItemsControl.Template>
<ControlTemplate>
<StackPanel>
<StackPanel>
<TextBlock Text="this is a title" FontSize="15" />
<TextBlock Text="This is a description" />
</StackPanel>
<ScrollViewer CanContentScroll="True" Height="400px">
<VirtualizingStackPanel IsItemsHost="True" />
</ScrollViewer>
</StackPanel>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
The code behind is :
public partial class Page1: Page
{
public List<string> Names { get; set; }
public Page1()
{
InitializeComponent();
Names = new List<string>();
for(int i = 0; i < 10000; i++)
Names.Add("Name : " + i);
My.DataContext = this;
}
}
As I force the ScrollViewer height to 400px, ItemsControl virtualization works as I expect: The ItemsControl displays the list very quickly, regardless of how many items it contains.
However, if I remove Height="400px", the list will expand its height to display the whole list, regardless its parent container height. Worse: it appears behind its container.
Putting a scrollviewer around the ItemsControl gives the expected visual result, but the virtualization goes away and the list takes too much time to display.
How can I achieve both automatic height expansion and virtualization of my ItemsControl ?

Answer 1

The problem is in the ItemsControl.Template: you use StackPanel there, which gives her children as much height as they want. Replace it to something like
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<StackPanel>
<TextBlock Text="this is a title" FontSize="15" />
<TextBlock Text="This is a description" />
</StackPanel>
<ScrollViewer CanContentScroll="True" Grid.Row="1">
<VirtualizingStackPanel />
</ScrollViewer>
</Grid>
And it should work fine.
Hope it helps.