当 ObservableCollection 中的 object 属性发生变化时，通知另一个属性 CommunityToolkit Mvvm

Question

Class definition:

    public partial class Pozycje: ObservableObject
    {
        [ObservableProperty] private bool _ok;
        [ObservableProperty] private string _name;
        [ObservableProperty] private decimal _qty;
        [ObservableProperty] private decimal _val;
    }

Collection and property definition:

public decimal Suma => Pozycja.Where(x => x.Ok).Sum(x=>x.Val+x.Qty);

private ObservableCollection<Pozycje> _poz;
public ObservableCollection<PozycjaObservable> Poz
{
    get => _poz;
    set
    {
      _poz = value;
      OnPropertyChanged();
      OnPropertyChanged(nameof(Suma));
   }
}

In Xaml:

 <Label Text="{Binding Suma}"/>

When I change "Poz" collection item property "Ok" Suma don't update.

Answer 1

Poz s setter is only called when Poz is assigned, NOT when items are added/removed

if you want to update Suma when an item is added or removed from Poz , you need to use Poz s CollectionChanged event

Poz.CollectionChanged += {
  OnPropertyChanged(nameof(Suma));
}