How do I listen to click events on all the tree nodes through the parent tree?

Instead of setting up event handlers on all the tree nodes you can listen to those events as they bubble up to the tree as follows:

[XAML]

<TreeView TreeViewItem.Selected="TvItem_Selected">
            <TreeViewItem>Node1</TreeViewItem>
            <TreeViewItem>Node2</TreeViewItem>
            <TreeViewItem>Node3</TreeViewItem>
            <TreeViewItem>Node4</TreeViewItem>
</TreeView>

Or you can setup the same thing in code as follows:

[C#]
treeView1.AddHandler(TreeViewItem.SelectedEvent, new RoutedEventHandler(TvItem_Selected));

The event handler would then be something like:

private void TvItem_Selected(object sender, RoutedEventArgs e)
{
	TreeViewItem item = e.Source as TreeViewItem;
            
	....
}