Demo_Validation/MainWindow.axaml.cs

using System.Collections.Generic;
using Avalonia.Controls;
using Avalonia.Interactivity;

namespace AvaloniaValidationSample;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        var listItem = new List<AvaloniaValidationSample.Item>()
        {
            new AvaloniaValidationSample.Item()
            {
                Id = 1,
                Password = "123",
                Text = "12345"
            },new AvaloniaValidationSample.Item()
            {
                Id = 1,
                Password = "123",
                Text = "12345"
            },new AvaloniaValidationSample.Item()
            {
                Id = 2,
                Password = "333",
                Text = "55"
            },new AvaloniaValidationSample.Item()
            {
                Id = 3,
                Password = "444",
                Text = "66"
            },

        };
        ItemsListBox.ItemsSource = listItem;
    }

    private void AddItem_OnClick(object? sender, RoutedEventArgs e)
    {
        new AddItem().ShowDialog(this);
    }
}