Why can't I select a null value in a ComboBox?

Question

In WPF, it seems to be impossible to select (with the mouse) a \"null\" value from a ComboBox. Edit To clarify, this is .NET 3.5 SP1.

Here\'s some c

Answer 1

Just a guess, but I think it sounds reasonable.

Assume combobox is using "ListCollectionView" (lcv as its instance) as its item collection, which it should be. If you are a programmer, what you gonna do?

I will respons to both Keyboard and Mouse.

Once I get Keyboard input, I use

lcv.MoveCurrentToNext();

or

lcv.MoveCurrentToPrevious();

So, sure keyboard works well.

Then I am working on respons Mouse inputs. And it comes the problem.

1. I want to listen 'MouseClick' event of my item. But probably, my Item doesn't generated, it is just a placeholder. So when user click on this placeholder, I get nothing.

2. If I get the event successfully, what's next. I will invoke

   lcv.MoveCurrentTo(selectedItem);

the "selectedItem" which would be null is not an acceptable parameter here I think.

Anyway, it's just guessing. I don't have time to debug into it though I am able to. I have a bunch of defects to fix. Good Luck. :)