I need to set the drag drop e.Effects to Copy depending on the format that is being dropped onto the editor, such that it displays the Copy cursor with a + sign when dragging over the editor. I'm trying to set e.Effects to Copy in PreviewDragOver, however the NotifyDragOver in DragDropManager will always overwrite my e.Effects as it uses the e.AllowedEffects to determine whether a Move is allowed. e.AllowedEffects is determined by the drag source and is readonly.
If I put e.Handled to true in PreviewDragOver, I get the copy effect I want but it doesn't go into DragDropManager.NotifyDragOver to display the drop caret in the right position.
For the actual Move/Copy behavior, I am able to set it to Copy in PasteDragDrop by setting e.DragEventArgs.Effects, however the cursor is still the Move cursor.
If a source allows both move and copy, the drag target should have control over whether to move or copy the element.