Please be so kind as to read my full post before responding. Thank you for your consideration.
The List Box control has an option "Allow multiple selection" (SelectMultiple). However, this is currently without much use, since the List Box is unable to display the result of such a multiple selection. For pre-selection, List Box only offers the "Default" (Default) property.
Please add the "DefaultSelectedItems" property (as in Combo Box) to List Box controls.