VirtualTreeView
	A WPF TreeView that actually supports virtualization. Works with .NET Framework 4.5.

It is available as a NuGet package.
The source code includes a demonstration application, where both modes (content and binding) are showed, side-by-side to traditional TreeView control.

It works exactly as the original TreeView (with a lot of missing features...):

<vtv:VirtualTreeView ItemsSource="{Binding Items}">
    <!-- Item style, if there is only one, can also be set using the ItemStyle property -->
    <vtv:VirtualTreeView.Resources>
        <!-- The important stuff here is the ItemsSource -->
        <HierarchicalDataTemplate ItemsSource="{Binding Children}" 
                                  DataType="{x:Type my:ViewModels}">
            <Grid>
                <TextBlock Text="{Binding MyLabel}"/>
            </Grid>
        </HierarchicalDataTemplate>
    </vtv:VirtualTreeView.Resources>
    <!-- This is optional if you want to bind the IsExpanded property -->
    <vtv:VirtualTreeView.ItemContainerStyle>
        <Style TargetType="{x:Type vtv:VirtualTreeViewItem}">
            <Setter Property="IsExpanded" Value="{Binding MyIsExpanded, Mode=TwoWay}" />
        </Style>
    </vtv:VirtualTreeView.ItemContainerStyle>
</vtv:VirtualTreeView>

If you move from an existing treeView, you'll need to copy/paste your TreeViewItem style and adapt it to vtv:TreeViewItem (usually no change is required, except removing the hierarchical part, which is generated when the control converts the tree to a list).

Currently it has only the features I needed (which is showing items and let them live); all contributors are welcome. The goal is to have a complete and extensible tree view.

• With binding, INotifyCollectionChanged fully works, so you can dynamically change content by adding or removing elements at any point of the hierarchy.

• With binding, INotifyPropertyChanged does not work at all, since the binding is partly simulated (because the view items are not generated).

Fork it, update it, and submit your pull requests.
Alternatively you can submit requests.