将List <T>转换为ObservableCollection <T>?
orderDetailView.boxLabels = new ObservableCollection<T_BoxLabel>((IEnumerable<T_BoxLabel>)_boxLabelService.GetBoxLabelsByOrderID(orderId));
orderDetailView.boxLabels = new ObservableCollection<T_BoxLabel>((IEnumerable<T_BoxLabel>)_boxLabelService.GetBoxLabelsByOrderID(orderId));