Xceed Datagrid virtualizing mode issue

Question

I have a very strange issue in wpf extended toolkit datagrid.

If I use a normal binding, all OK:

<xcdg:DataGridControl ItemsSource="{Binding DbTags.Local}"/>

But in virtualizing mode text is invisible, but rows is exist.

<Grid.Resources>
    <xcdg:DataGridVirtualizingQueryableCollectionViewSource x:Key="QueryableViewSource" QueryableSource="{Binding Path=DbTags}"/>
</Grid.Resources>

<xcdg:DataGridControl ItemsSource="{Binding Source={StaticResource QueryableViewSource}}"/> 

Screen

Thank You for helping

Answer 1

It is strange, but all work properly with sort "OrderBy" or "OrderByDescending".

If I set QueryableSource to DbSet without sort or other query, text is hided.

public IQueryable<DB.Tag> DbTags
        {
            get
            {
                return _localTagsContext.Tags.OrderByDescending(x =>x.Num);
            }
        }