GazpromApp/App.axaml.cs

using System.Linq;
using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Data.Core.Plugins;
using Avalonia.Markup.Xaml;
using GazpromApp.Utils;
using GazpromApp.ViewModels;
using GazpromApp.Views;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;

namespace GazpromApp;

public class App : Application
{
    private static ServiceProvider? Services { get; set; }
    
    public override void Initialize()
    {
        AvaloniaXamlLoader.Load(this);
    }

    public override void OnFrameworkInitializationCompleted()
    {
        var services = new ServiceCollection();

        services.AddDbContext<AppDbContext>(options =>
        {
            var dbPath = new AppDbContext().DbPath;
            options.UseSqlite($"Data Source={dbPath}");
        });
        
        services.AddTransient<MainWindowViewModel>();
        
        Services = services.BuildServiceProvider();
        
        var dbContext = Services.GetRequiredService<AppDbContext>();
        dbContext.Database.EnsureCreated();
        
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            DisableAvaloniaDataAnnotationValidation();
            desktop.MainWindow = new MainWindow
            {
                DataContext = Services.GetRequiredService<MainWindowViewModel>()
            };
        }

        base.OnFrameworkInitializationCompleted();
    }

    private void DisableAvaloniaDataAnnotationValidation()
    {
        // Get an array of plugins to remove
        var dataValidationPluginsToRemove =
            BindingPlugins.DataValidators.OfType<DataAnnotationsValidationPlugin>().ToArray();

        // remove each entry found
        foreach (var plugin in dataValidationPluginsToRemove)
        {
            BindingPlugins.DataValidators.Remove(plugin);
        }
    }
}