为什么我的对象在事件中缺少属性？

I have in WPF, using devexpress, a situation where I have a DragDropManager with the event handler in code-behind. When I drag a row onto the grid control, the event handler is called as expected. My problem is that the control wrapped inside the event args has most of its defining properties replaced by question marks '?', so I can't really get any identifying information from the source control (from which I dragged the row). I have in WPF, using devexpress, a situation wh