public class TreeViewItemEx : TreeViewItem
    {
        internal static TreeViewItemEx CreateBindings()
        {
            TreeViewItemEx tvi = new TreeViewItemEx();

            Binding expandedBinding = new Binding("IsExpanded");
            expandedBinding.Mode = BindingMode.TwoWay;
            tvi.SetBinding(TreeViewItemEx.IsExpandedProperty, expandedBinding);

            Binding selectedBinding = new Binding("IsSelected");
            selectedBinding.Mode = BindingMode.TwoWay;
            tvi.SetBinding(TreeViewItemEx.IsSelectedProperty, selectedBinding);

            return tvi;
        }

        protected override DependencyObject GetContainerForItemOverride()
        {
            return CreateBindings();
        }
    }

    public class TreeViewEx : TreeView
    {
        protected override DependencyObject GetContainerForItemOverride()
        {
            return TreeViewItemEx.CreateBindings();
        }
    }