Changing visibility of ToolbarItem - Xamarin.Forms

I want to fill collection of ToolbarItems from XAML, but change visibility of some ToolbarItem from view model.

I implemented BasePage with some wrapper around ToolbarItems collection:

public class BasePage : ContentPage
{
    public IList CustomToolbar { get; private set; }

    public BasePage()
    {
        var items = new ObservableCollection();
        items.CollectionChanged += ToolbarItemsChanged;

        CustomToolbar = items;
    }

    private void ToolbarItemsChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        ToolbarItems.Clear();

        foreach (var item in CustomToolbar)
        {
            item.PropertyChanged += OnToolbarItemPropertyChanged;
            if (item.IsVisible)
            {
                ToolbarItems.Add(item);
            }
        }
    }

    private void OnToolbarItemPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == CustomToolbarItem.IsVisibleProperty.PropertyName)
        {
            UpdateToolbar();
        }
    }

    private void UpdateToolbar()
    {
        foreach (var item in CustomToolbar)
        {
            if (item.IsVisible)
            {
                ToolbarItems.Add(item);
            }
            else
            {
                ToolbarItems.Remove(item);
            }
        }
    }

    protected override void OnDisappearing()
    {
        base.OnDisappearing();

        ToolbarItems.Clear();
        CustomToolbar.Clear();
        foreach (var item in CustomToolbar)
        {
            item.PropertyChanged -= OnToolbarItemPropertyChanged;
        }
    }
}

CustomToolbarItem.cs:

```
public class CustomToolbarItem : ToolbarItem
{
public static readonly BindableProperty IsVisibleProperty =
BindableProperty.Create(nameof(IsVisible),
typeof(bool),
typeof(CustomToolbarItem),

Two things:

-
You clear ToolbarItems and CustomToolbar when page dissapearing, this causes problem: when you show next page and then go back, you won't see your items anymore, because they were cleared.

-
Handlers OnToolbarItemPropertyChanged will not be removed in foreach cycle, because you clear list before this cycle.

StackExchange Code Review Q#135481, answer score: 3