I have a tabViewModel that has a Parent property. This property is updated from the Observable OnChanged event, so that the parent is updated to whatever MainViewModel the tab is dragged to. But when docking/branching the tab in a window, it seems to not run the onchanged event in the observable collection. So I am trying to set the Parent property using the DragablzItem.DragCompleted, but I am having a hard time accessing the actual tabviewmodel from that event. All i can see is a UnderlyingContent that contains the tabViewModel instance, but that property is internal. Is there a way to do this using this event, or am i looking in the wrong place?