Why is my listView not updating after changing itemsource?

Question

I have a listview which receives information from a HashSet, but when I delete one item of the HashSet, my listview is not updated.

And my listview doesn't have a method of refresh, don't know why. Here is my code:

private void deleteActivityFromAlumn(String activityName, String nif)
{
    Alumn alumnDelete = Alumn.findAlumnByNIF(nif);
    Activity activityDelete = Activity.getActivityByName(activityName);
    Debug.WriteLine(alumnDelete.Name + activityDelete.Name);
    alumnDelete.activities.Remove(activityDelete);
    activityDelete.Alumns.Remove(alumnDelete);
    listActivities.ItemsSource = alumnDelete.activities;
}

And the item is deleted in a right way because if I go search for the object again, it is removed from the listView, but I believe that its supposed to be updated when you refresh the ItemsSource.

Answer 1

To make sure that control with bound items changes when those items change you have to

1. Either make that collection implement INotifyCollectionChanged . The simplest way to do it is to use ObservableCollection<T> instead of HashSet<T>
   • Though you will lose the uniqueness property that HashSet<T> gives you.
2. Or to somehow force a refresh of that control when you change the collection. Though one has to take into account that it is not the best solution , as it will more often than not cause a full redrawing of the control with obvious performance and/or display issues .
   • Either by calling the Refresh method ( WPF , WinForms )
   • Or by re-binding the collection

listActivities.ItemsSource = null; 
listActivities.ItemsSource = alumnDelete.activities