Can I control which nodes are selectable in a WPF TreeView?

Question

I have a two-level hierarchy displayed in a WPF TreeView, but I only want the child nodes to be selectable - basically the top level nodes are for categorisation but shouldn't be selectable by themselves.

Can I achieve this?

Thanks...

Answer 1

To do so you would need to override the style for treeview. Ideally you will have two types of treeview items one for your top-level nodes (im assuming folders) and another simply for the children, then you should be able to define how each item type in the tree behaves. So create a style for each item type, then for the folder node simply change the trigger for is selected to do nothing.

Answer 2

I've written at attached property that will unselect a treeviewitem as soon as it's selected:

public class TreeViewItemHelper
{
    public static bool GetIsSelectable(TreeViewItem obj)
    {
        return (bool)obj.GetValue(IsSelectableProperty);
    }

    public static void SetIsSelectable(TreeViewItem obj, bool value)
    {
        obj.SetValue(IsSelectableProperty, value);
    }

    public static readonly DependencyProperty IsSelectableProperty =
        DependencyProperty.RegisterAttached("IsSelectable", typeof(bool), typeof(TreeViewItemHelper), new UIPropertyMetadata(true, IsSelectablePropertyChangedCallback));

    private static void IsSelectablePropertyChangedCallback(DependencyObject o, DependencyPropertyChangedEventArgs args)
    {
        TreeViewItem i = (TreeViewItem) o;
        i.Selected -= OnSelected;
        if(!GetIsSelectable(i))
        {
            i.Selected += OnSelected;
        }
    }

    private static void OnSelected(object sender, RoutedEventArgs args)
    {
        if(sender==args.Source)
        {
            TreeViewItem i = (TreeViewItem)sender;
            i.IsSelected = false;
        }
    }
}

Unfortunately you still lose the old selection when you click on an unselectable item :(