Not Refreshing Spesific Label While Binding ObservableCollection Listview in Xamarin & MVVM

My INotifyPropertyChanged Code:

public class Zicker : INotifyPropertyChanged
{
public class MyClass
{
public string HeyName { get; set; }
public string HeySurname { get; set; }
public int HeyAge { get; set; }
}

    public event PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged([CallerMemberName] string name = null)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged.Invoke(this, new PropertyChangedEventArgs(name));
        }
    }

    private ObservableCollection<MyClass> _yourList = new ObservableCollection<MyClass>();
    public ObservableCollection<MyClass> YourList
    {
        get
        {
            return _yourList;
        }
        set
        {
            _yourList = value;
            RaisePropertyChanged("YourList");
            RaisePropertyChanged("BindMeLabel");
        }
    }

    public int BindMeLabel
    {
        get { return _yourList.Sum(a => a.HeyAge); }
    }

    public void WonCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        RaisePropertyChanged("BindMeLabel");
    }

    public List<string> heresamplenames = new List<string> { "Mohamed", "Zaran", "Ivan" };
    public List<string> heresamplesurnames = new List<string> { "Pakou", "Simmone", "Zagoev" };
    public List<int> heresampleages = new List<int> { 17,33,50 };

    public Zicker()
    {
        ObservableCollection<MyClass> vs = new ObservableCollection<MyClass>();
        for (int i = 0; i < 3; i++)
        { vs.Add(new MyClass { HeyName = heresamplenames[i], HeySurname = heresamplesurnames[i], HeyAge = heresampleages[i] }); }
        YourList = vs; YourList.CollectionChanged += WonCollectionChanged;
    }
}

My XAML.CS

    public MainPage()
    {
        InitializeComponent();
        BindingContext = new Zicker();
    }

My XAML:

<ContentPage.Content>



<ListView.ItemTemplate>


<ViewCell.View>

<Grid.ColumnDefinitions>



</Grid.ColumnDefinitions>




</ViewCell.View>


</ListView.ItemTemplate>




</ContentPage.Content>

My Problem:

In List, there are three names, surnames, and ages. At the bottom, there is also a label which should be shown as the sum of Ages collection.

When the UI is starting, Label is working well. But, if I try to change any Ages entries, there is a big problem with the binding label.