Custom NSDocument, Custom NSWndowController Undo action not working

Hi,

I have a document-based app with NSWindowController subclassed as described here. All is working except UndoManager.

In my subclassed NSDocument, I am doing the following;

this.UndoManager.RegisterUndoWithTarget (this, performUndoUpdate, updateItem);
this.UndoManager.SetActionname ("Undo Update");

My MainMenu undo menu item title does not change and clicking 'Undo' does not call the provided redo action. If I try to close the document, it'll prompt for unsaved changes to be saved, so I know the UndoManager is working somewhat, the issue seems to be with menu items action not being triggered.

I think I'm missing something somewhere. Is the NSWindowController subclass meant to handle any thing???

Many Thanks..