Can't scroll TreeView inside a ScrollViewer

Question

I've a TreeView inside a ScrollViewer. When I turn the mouse wheel on the treeview, treeview is not sliding and it stays at the same point. But when I move the scrollbar, I can slide the treeview.

I'm pretty sure that treeview has a scrollviewer but my point is to use an other scrollviewer is, I've a scrollviwer template and I used this template all over my app. That's why I want to use this template again.

Here is the code:

<ScrollViewer Template="{DynamicResource AppleStyleScrollBarStyle}">
    <TreeView>
        <TreeViewItem Header="TreeViewItem"/>
        <TreeViewItem Header="TreeViewItem"/>
        <TreeViewItem Header="TreeViewItem"/>
        <TreeViewItem Header="TreeViewItem"/>
      </TreeView>
</ScrollViewer>

Answer 1

This answer helped me: WPF Remove ScrollViewer from TreeView

https://serialseb.com/blog/2007/09/03/wpf-tips-6-preventing-scrollviewer-from/

Just subscribe to your treeView's PreviewMouseWheel event:

    // https://serialseb.com/blog/2007/09/03/wpf-tips-6-preventing-scrollviewer-from/
    private void treeView_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
    {
        if (sender is TreeView && !e.Handled)
        {
            e.Handled = true;
            var eventArg = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta);
            eventArg.RoutedEvent = UIElement.MouseWheelEvent;
            eventArg.Source = sender;
            var parent = ((Control)sender).Parent as UIElement;
            parent.RaiseEvent(eventArg);
        }
    }

Answer 2

TreeView default template already contains ScrollViewer. When you wrap it in another ScrollViewer the one inside TreeView does nothing but still handles some mouse events like mouse wheel. Instead you can create implicit Style for ScrollViewer in TreeView.Resources

<TreeView>
    <TreeView.Resources>
        <Style TargetType="{x:Type ScrollViewer}">
            <Setter Property="Template" Value="{DynamicResource AppleStyleScrollBarStyle}"/>
        </Style>
    </TreeView.Resources>
    <TreeViewItem Header="TreeViewItem"/>
    <TreeViewItem Header="TreeViewItem"/>
    <TreeViewItem Header="TreeViewItem"/>
    <TreeViewItem Header="TreeViewItem"/>
</TreeView>