Property changes with multiple objects selected is not undo-able.

The winforms propertygrid natively supports selecting more than one object, and being able to set a given property on them all at the same time if that property is the same type/name.

However, the only event it exposes for responding to such a change is OnPropertyValueChanged which occurs after the new value is already set, and does not pass what the previous value was, if there is more than one object selected.

So, implementing this means we probably need to store the state of all objects in the selection, whenever the selection is changed, then push THAT state into the undo/redo object when OnPropertyValueChanged occurs.