Question

I have a TreeView control, and after a new node is added, I need to execute some custom code (ex expand the node, make it visible, and fire begind edit method). Since I want this to be available in every instance of TreeView control, I thought of subclassing the TreeView control.

Now, in order for treeview to know when the new node is added, it would either have an event that is fired when item is added (which it doesn’t), or to have a reference to command that was executed to add a new item.

So two questions:

1) Is there a way to add an event in TreeView that would be fired whenever a treenode is added (I am always adding nodes through source collection from ViewModel) – I could not find any way to do this

2) I could add an AddCommand property to TreeList, that would be bound to ViewModel’s AddCommand, and then have some button, or ContextMenu item that would bind to TreeList.AddCommand, instead of view model. This way TreeView would hold reference to AddCommand, but the drawback would be that actual usage would be kind of wierd. Question: How can I know when an TreeView’s AddCommand (or any command, to that matter) is executed, so I can fire some custom code after it? It seems that CommandManager.AddExecutedHandler is a solution, but I am unable to execute it.

Answer 1

Is this any help?

public class CustomTreeControl : TreeView
{
    ...

    // WPF only
    protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
    {
        base.OnItemsSourceChanged(oldValue, newValue);

        Debug.WriteLine("OnItemsSourceChanged");
    }

    // WPF + Silverlight
    protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
    {
        base.OnItemsChanged(e);

        Debug.WriteLine("OnItemsChanged: {0}", e.Action);
    }
}