private static void SelectedItemsOnCollectionChanged(SelectCrossRefViewModel vm, object sender, NotifyCollectionChangedEventArgs args)
 {
     vm.HasErrors = vm._limitSelectedItems && vm._maxSelectedItems > 1 && vm.SelectedItems.Count > vm._maxSelectedItems;
 }
 private void ApplyFilter(SelectCrossRefViewModel vm)
 {
     vm.ColumnFilter = PrepareFilter();
     vm.Refresh();
 }