CarouselView.PagerIndicatorDots.cs

void ItemsSourceChanged ()
{
    if (ItemsSource == null) return;

    var countDelta = ItemsSource.Count - Children.Count;

    if (countDelta > 0) {
        for (var i = 0; i < countDelta; i++) 
        {
            CreateDot();
        }
    } 
    else if (countDelta < 0) 
    {
        for (var i = 0; i < -countDelta; i++) 
        {
            Children.RemoveAt (0);
        }
    }
}

public PagerIndicatorDots()
{
    HorizontalOptions = LayoutOptions.CenterAndExpand;
    VerticalOptions = LayoutOptions.Center;
    Orientation = StackOrientation.Horizontal;
    DotColor = Color.Black;
}

void CreateDot()
{
    //Make one button and add it to the layout
    var dot = new Button {
        BorderRadius = Convert.ToInt32(DotSize/2),
        HeightRequest = DotSize,
        WidthRequest = DotSize,
        BackgroundColor = DotColor
    };
    Children.Add(dot);
}