How to change the text of a BarButtonItem on the NavigationBar?

I am trying to create a list of items that can be edited. Something like this:

To that end, I added a NavigationBar to the top of the view, then added 2 Bar Button Items in XCode designer. I set the identifier for the button on the left to Add, for the button on the right to Edit.

When I click the Edit, I want to change the text to Done. I've tried various ways, e.g. btnEdit.Title = "Done", but it simply doesn't take.

I've seen several blog posts recommending .SetTitle, but UIButtonBarItem doesn't have that method (at least in MonoTouch).

So, how can I change the title of the Edit button?

I resolved it. The key was I was setting the identifier of the Edit button to a system value (e.g. UIBarButtonSystemItemEdit) and you can't change the text of those (makes sense now). I changed the identifier back to Custom and setting .Title worked fine.