CollectionViewSource grouping, get sum(Quantity)

Question

I have a CollectionViewSource whose source is an ObservableCollection.

On a List or ObservableCollection, I can use linq to group my objects, and sum their quantities, but how is it possible to do it on a CollectionViewSource(if it is possible), I see nowhere any documentation about it.

For now I only can manage grouping using :

ProductsView.GroupDescriptions.Add(new PropertyGroupDescription("Group"));

But I see nowhere information on how to display a sum, or maximum/minimum value of a field?

Edit :

Concretely, I want to do equivalent of that :

liste_ass = liste_ass.GroupBy(l => l.Name)
     .Select(cl => new Assemblage
     {
         Quantite = cl.Sum(c => c.Quantite),
         ID = 0,
         IdAffaire = cl.First().IdAffaire,
         Name = cl.First().Name,
         Priorite = 0,
         Dessin = cl.First().Dessin,
         Groupe = cl.First().Groupe,
         Priorite = cl.Max(c=>c.Priorite),
         ListeIdOperations = cl.First().ListeIdOperations,
     }).ToList();

This is what I would do in linq. But reading about ICollectionView, it seems this is not possible to do that on ICollectionView, as it is a view, and no operation can be done on them.

Answer 1

You can access every CollectionViewGroup which contains all the group's imformation including ItemCount through CollectionView.Groups property. If you want to create a custom group header and show it on UI, here is a sample:

    <ListBox ItemsSource="{Binding your view}">
         <ListBox.Resources>
             <local:ToAssemblageConverter x:Key="toAssemblageConverter"/>
         </ListBox.Resources>
         <ListBox.GroupStyle>
            <GroupStyle HidesIfEmpty="True">
                <GroupStyle.HeaderTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal"
                                    DataContext="{Binding Items, Converter={StaticResource ResourceKey=toAssemblageConverter}}">
                            <TextBlock Margin="5 0" Text="{Binding Quantite}"/>
                            <TextBlock Margin="5 0" Text="{Binding Id}"/>
                            ...
                        </StackPanel>     
                    </DataTemplate>
                </GroupStyle.HeaderTemplate>
            </GroupStyle>
        </ListBox.GroupStyle>           
    </ListBox>

public class ToAssemblageConverter : IValueConverter
{
    public object Convert (object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var cl = (IEnumerable)value;

        return new Assemblage() {
            Quantite = cl.Sum(c => c.Quantite),
            ID = 0,
            IdAffaire = cl.First().IdAffaire,
            Name = cl.First().Name,
            Priorite = 0,
            Dessin = cl.First().Dessin,
            Groupe = cl.First().Groupe,
            Priorite = cl.Max(c=>c.Priorite),
            ListeIdOperations = cl.First().ListeIdOperations,
        }
    }
}