UpdateSourceTrigger PropertyChanged on IsChecked Isn't Firing on ItemsSource of ListBox of Checkboxes

Question

I have a listbox in which the item source contains a List(of T) that has a SelectedFlag boolean property. My viewmodel is set as the DataContext of my user control and ever

Answer 1

You'll need to make your Collection's CollectionChanged event fire when your Item's PropertyChanged event fires.

Something like:

MyCollection.CollectionChanged += MyCollectionChanged;

...

void MyCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    if (e.NewItems != null)
    {
        foreach (object item in e.NewItems)
        {
            if (item is MyItem)
                ((MyItem)item).PropertyChanged += MyItem_PropertyChanged;
        }
    }

    if (e.OldItems != null)
    {
        foreach (object item in e.OldItems)
        {
            if (item is MyItem)
                ((MyItem)item).PropertyChanged -= MyItem_PropertyChanged;
        }
    }
}

...

void MyItem_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    OnPropertyChanged("MyCollection");
}