sum of filtered ICollectionView - wpf

Question

suppose this base class
public class Contrat_Paye_Item
{
public int CPI_TYPE { get; set; }
public string CPI_TEXT { get; set; }
public decimal CPI_AMOUNT { get; set; }
}
in my view Model i have made a list from that class like this :
private ObservableCollection<Contrat_Paye_Item> listapayer;
public ObservableCollection<Contrat_Paye_Item> ListaPayer
{
get
{
return listapayer;
}
set
{
listapayer = value;
OnPropertyChanged("ListaPayer");
}
}
and in the VM constructor, just some testdata :
listapayer.Add(new Contrat_Paye_Item()
{
CPI_TYPE = 0,
CPI_TEXT = "Loyer",
CPI_AMOUNT = 100
});
listapayer.Add(new Contrat_Paye_Item()
{
CPI_TYPE = 1,
CPI_TEXT = "charge 1",
CPI_AMOUNT = 200
});
listapayer.Add(new Contrat_Paye_Item()
{
CPI_TYPE = 1,
CPI_TEXT = "Charges 2",
CPI_AMOUNT = 300
});
so the full list contain 3 item, the total Amount is 600 .
in my viewmodel i have added a sublist with only items that their CPI_TYPE = 1 and bound it to a listbox without problem like this :
public ICollectionView ListCharges
{
get
{
var sub= new CollectionViewSource { Source = listapayer }.View;
sub.Filter = p => (p as Contrat_Paye_Item).CPI_TYPE == 1;
return sub;
}
}
now what i want to display is a list of my items , with a row that contain a sum of amounts items of the sublist . a bind it to a second listbox
something like :
loyer 100
charges 500
any idea, tip is welcome .
thanks

Answer 1

How about adding something like this before returning the sub:
var d1 = (from a in sub.SourceCollection.OfType<Contrat_Paye_Item>() where a.CPI_TEXT == "Loyer" select a.CPI_AMOUNT).Sum();
var d2 = (from a in sub.SourceCollection.OfType<Contrat_Paye_Item>() where a.CPI_TEXT.ToLower().StartsWith("charge") select a.CPI_AMOUNT).Sum();
sub.AddNewItem(new Contrat_Paye_Item() { CPI_TEXT="Sum Loyer", CPI_AMOUNT = d1} );
sub.CommitNew();
sub.AddNewItem(new Contrat_Paye_Item() { CPI_TEXT = "Sum Charges", CPI_AMOUNT = d2 });
sub.CommitNew();
//Edit
Note this as a more flexible possibility:
Do not use _CollectionViewSource _. Instead use the following as the ItemsSource of the ListBox:
public ObservableCollection<Contrat_Paye_Item> ListCharges
{
get
{
return new ObservableCollection<Contrat_Paye_Item>((from a in listapayer where a.CPI_TYPE == 1 select a));
}
}