A typical scenario in many applications is to be able to be able to select
one or more objects in a list and then be able to edit one or more
properties of those objects at the same time.

Example: You have a list in one side of the dialog, bound to a datatable,
and you have a text box beside it. It is easy to bind the textbox to
propertyA of the item selected in the list. But if the user selects multiple
items, you only want the textbox to display the value if propertyA is the
same value for all selected objects in the list, and otherwise <blank>. If
the user changes anything in the text box, it should be reflected to all the
selected objects.

You can see examples of this in practically any Microsoft product I can
think of. Is this possible using databinding? Or is there no way around a
custom coding.