Question

1. How do I know whether or not my list is being virtualized?

2. How do I make this snippet virtualized?

   <ScrollViewer Grid.Column="1" Name="LogScroller">
       <r:NoInheritanceContentControl>
           <ListBox   Background="Black" ItemsSource="{Binding Path=ActiveLog}" >
               <ListBox.ItemTemplate>
                   <DataTemplate>
                       <Grid Background="Black">
                           <Grid.ColumnDefinitions>
                               <ColumnDefinition Width="200"></ColumnDefinition>
                               <ColumnDefinition Width="*"></ColumnDefinition>
                           </Grid.ColumnDefinitions>
                           <Grid.RowDefinitions>
                               <RowDefinition></RowDefinition>
                               <RowDefinition></RowDefinition>
                           </Grid.RowDefinitions>
                           <TextBlock Grid.Column="0" Grid.Row="0" Foreground="White">
                           <TextBlock >Date:</TextBlock>
                           <TextBlock  Text="{Binding Path=LogDate}"/>
                       </TextBlock>
                           <TextBlock Grid.Column="1" Grid.Row="0" Foreground="White">
                           <TextBlock >Severity:</TextBlock>
                           <TextBlock  Text="{Binding Path=Severity}"/>
                       </TextBlock>
                           <TextBlock Grid.Column="0" Grid.ColumnSpan="2" Grid.Row="1" Foreground="LightGray" Text="{Binding Path=Message}"></TextBlock>
                       </Grid>
                   </DataTemplate>
               </ListBox.ItemTemplate>
               <ListBox.Template>
                   <ControlTemplate>
                       <StackPanel Background="Black" IsItemsHost="True" >
                       </StackPanel>
                   </ControlTemplate>
               </ListBox.Template>
           </ListBox>
       </r:NoInheritanceContentControl>
   </ScrollViewer>
   

Answer 1

Your code sample does not virtualize because you are forcing the use of a StackPanel. You have to use a VirtualizingStackPanel.