How to disable selectability if more than two CollectionView Xamarin items are selected?

Question

C++ / C#

I have a ContentView and I want to get the number of selected items in it.
Also, how do I disable the ability to select if more than two items are selected?

public class ListViewEx1
{
    public string Text { get; set; }
    public int Num { get; set; }
}

var collectionView1_one = new CollectionView(){ 
    SelectionMode = SelectionMode.Multiple,
    ItemsSource = new List<ListViewEx1>() 
    {
        new ListViewEx1{ Text = "1) Onetext", Num = 1 },
        new ListViewEx1{ Text = "2) text", Num = 2 },
        new ListViewEx1 { Text = "3) ggfggf", Num = 3 },
        new ListViewEx1{ Text = "4) affff", Num = 4 },
        new ListViewEx1{ Text = "5) zzzzzzzz", Num = 5 },
    },
    ItemTemplate = new DataTemplate(() => 
    {
        Label titleLabel = new Label { FontSize = 18 }; 
        titleLabel.SetBinding(Label.TextProperty, "Text");

        return new StackLayout 
        {
                Orientation = StackOrientation.Vertical,
                Children = {
                    titleLabel
                }
        };
    })
};
StackLayoutMap.Children.Add(collectionView1_one);

Answer 1

https://docs.microsoft.com/ru-ru/xamarin/xamarin-f...
https://docs.microsoft.com/ru-ru/dotnet/api/xamari...
something tells me that collectionView1_one.SelectedItems.Count;
moreover, the banal IntelliSense of the visual studio, when entering a point, and viewing the options, it should show a
sin to ask such questions
ps and you can also press F1 on the data type. in your case CollectionView. and get links that at the beginning of the response