// EventsControl class

private bool Filter(object obj)
{
    if (!(obj is Event @event)) return false;
    if (string.IsNullOrEmpty(Location)) return true;

    return true;
    //  return @event.Location == Location;
}

public static readonly DependencyProperty EventsSourceProperty = DependencyProperty.Register(
    nameof(EventsSource), typeof(ObservableCollection<Event>), typeof(EventsControl), new PropertyMetadata(default(ObservableCollection<Event>), EventsSourceChanged));

public ObservableCollection<Event> EventsSource
{
    get => (ObservableCollection<Event>)GetValue(EventsSourceProperty);
    set => SetValue(EventsSourceProperty, value);
}

public ICollectionView EventsView { get; set; }

private static void EventsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    if (!(d is EventsControl eventsControl)) return;

    var view = new CollectionViewSource { Source = e.NewValue }.View;
    view.Filter += eventsControl.Filter;
    eventsControl.EventsView = view;
    //view.Refresh();
}