AvaloniaTaskNine/AvaloniaApplication2/ViewModels/PersonalVM.cs

using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Platform.Storage;
using AvaloniaApplication2.Models;
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AvaloniaApplication2.ViewModels
{
    internal class PersonalVM : ViewModelBase
    {
        User _user;
        public User User { get => _user; set => this.RaiseAndSetIfChanged(ref _user, value); }
        public PersonalVM(User user)
        {
            User = user;
        }

        public void Vixod()
        {
            MainWindowViewModel.Instance.Page = new AuthAndReg();
        }

        public async Task Image()
        {
            if (Application.Current?.ApplicationLifetime is not IClassicDesktopStyleApplicationLifetime desctop || desctop.MainWindow?.StorageProvider is not { } provider) throw new NullReferenceException("провайдер отсутствует");

            var file = await provider.OpenFilePickerAsync(
                new FilePickerOpenOptions()
                {
                    Title = "Выберите изображение",
                    AllowMultiple = false,
                    FileTypeFilter = [FilePickerFileTypes.All, FilePickerFileTypes.ImageAll]
                }
                );
            if (file != null)
            {
                await using var readStream = await file[0].OpenReadAsync();
                byte[] buffer = new byte[readStream.Length];
                readStream.ReadAtLeast(buffer, 1);
                User.Image = buffer;
                MainWindowViewModel.myconnection.Users.Update(User);
                MainWindowViewModel.myconnection.SaveChanges();
                MainWindowViewModel.Instance.Page = new Personal(User);
            }
        }
    }
}