Picker's SelectedItem in CollectionView DataTemplate not working

[gwalus]

Can someone explain me why the single picker binds data correctly and when i put in to CollectionView its doesn't works.

I would to populate data to pickers immidientialy.

When i click button to force refresh, values show in UI - but it's bad.

I don't know it's a bug or i make it bad.

Here is my code:

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MauiApp1.MainPage"
             xmlns:viewModels="clr-namespace:MauiApp1.ViewModels"
             x:DataType="viewModels:MainPageViewModel">

    <VerticalStackLayout Spacing="25" Margin="10">
        <Label Text="Single Picker" TextColor="Red"/>
        <Picker 
            ItemsSource="{Binding Numbers}"
            SelectedItem="{Binding SelectedNumber}"/>

        <Label Text="Picker in CollectionView" TextColor="Red"/>
        <CollectionView ItemsSource="{Binding Products}">
            <CollectionView.ItemTemplate>
                <DataTemplate x:DataType="viewModels:Product">
                    <VerticalStackLayout>
                        <Label Text="{Binding Name}"/>

                        <Picker ItemsSource="{Binding Source={x:RelativeSource AncestorType={x:Type viewModels:MainPageViewModel}}, Path=Numbers}"
                                SelectedItem="{Binding Quantity}"/>
                    </VerticalStackLayout>
                </DataTemplate>
            </CollectionView.ItemTemplate>
        </CollectionView>

        <Label Text="Force refresh picker value" TextColor="Red"/>
        <Button Text="Refresh" Command="{Binding ButtonCommand}"/>
    </VerticalStackLayout>
</ContentPage>

MainPage.xaml.cs

using MauiApp1.ViewModels;

namespace MauiApp1
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();

            BindingContext = new MainPageViewModel();
        }
    }
}

MainPageViewModel.cs

using System.ComponentModel;
using System.Windows.Input;

namespace MauiApp1.ViewModels
{
    public class MainPageViewModel : INotifyPropertyChanged
    {
        public MainPageViewModel()
        {
            ButtonCommand = new Command(OnButtonClicked);
        }

        public event PropertyChangedEventHandler? PropertyChanged;

        private int _selectedNumber = 5;
        public int SelectedNumber
        {
            get => _selectedNumber;
            set
            {
                _selectedNumber = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("SelectedNumber"));
            }
        }

        public List<int> Numbers { get; set; } = Enumerable.Range(1, 8).ToList();

        private List<Product> _products =
        [
            new Product { Name = "Product 1", Quantity = 2 },
            new Product { Name = "Product 2", Quantity = 5 }
        ];

        public List<Product> Products
        {
            get => _products;
            set
            {
                _products = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Products"));
            }
        }

        public ICommand ButtonCommand { get; }

        private void OnButtonClicked()
        {
            foreach (var product in Products)
            {
                product.Quantity = Random.Shared.Next(1, 8);
            }
        }
    }

    public class Product : INotifyPropertyChanged
    {
        private string _name;
        public string Name
        {
            get => _name;
            set 
            {
                _name = value; 
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Name))); 
            }
        }

        private int _quantity = 1;
        public int Quantity
        {
            get => _quantity;
            set
            {
                _quantity = value;
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Quantity)));
            }
        }

        public event PropertyChangedEventHandler? PropertyChanged;
    }
}

On start

After click refresh

Can someone helps?

[axa88]

This is a common issue, you need to initialize. All you've done is subscribe to changes, by the time your controls are displayed the property values are already set , no change occurs, no updates are made.

Call OnButtonClicked at the end of your constructor. or initialize otherwise