如何设置combox项可见性？

i have 2 WPF comboboxes(comboboxA, comboboxB)with identical combobox item(Apple & Orange). Let say i select "Apple" in the comboboxA, then the "Apple" need to be hidden in the comboxB. If i go back to comboxA and select "Orange", "Apple" will be visible and "Orange" need to be hidden. How can i achieve that using C#?i have 2 WPF comboboxes(comboboxA, comboboxB)wi