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

ComboBox needs a DataTemplate to display the item no matter how simple it is. DataTemplate works like this: get a value from instance.[path], e.g.

bar1.Car.Color

So it cannot get a value from

null.Car.Color

It will throw a null reference exception. So, the null instance will not be displayed. But the the Color - if it is a reference type - is allowed to be null because there will be no exception in this case.