Сакутин_сериализация в хранилище

using System;
using System.Collections.Generic;
using System.Threading;
using System.Linq;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;

namespace IMJunior
{
    class Program
    {
        static UserRepository _users = new UserRepository();

        static void Main()
        {
            while (true)
            {
                string command = Console.ReadLine();
                switch (command)
                {
                    case "Update":
                        Console.WriteLine("Id:");
                        int id = Convert.ToInt32(Console.ReadLine());
                        Console.WriteLine("Name:");
                        string name = Console.ReadLine();
                        Console.WriteLine("Money:");
                        float money = (float)Convert.ToDouble(Console.ReadLine());
                        Console.WriteLine(UpdateUser(id, name, money));

                        break;
                    case "Create":

                        Console.WriteLine("Name:");
                        string name2 = Console.ReadLine();
                        Console.WriteLine("Money:");
                        float money2 = (float)Convert.ToDouble(Console.ReadLine());
                        Console.WriteLine(CreateUser(name2, money2));

                        break;
                    case "Show":
                        Console.WriteLine(ShowUsers());
                        break;
                }
            }
        }

        static string UpdateUser(int id, string name, float? money)
        {
            User user = _users.GetById(id);
            if (user == null) return "Вы не можете обновить это пользователя";

            if (name != null)
            {
                user.Name = name;
            }
            if (name != null)
            {
                user.Money = (float)money;
            }

            return "Обновление прошло успешно";
        }

        static string CreateUser(string name, float money)
        {
            User user = _users.Create();

            user.Name = name;
            user.Money = money;

            return "Пользователь создан";
        }

        static string ShowUsers()
        {
            StringBuilder response = new StringBuilder();

            foreach (var user in _users.GetAll())
            {
                response.Append($"[{user.Id}] {user.Name} - {user.Money}\n");
            }

            return response.ToString();
        }
    }

    class UserRepository
    {
        private readonly List<User> _users = new List<User>();

        public UserRepository()
        {
            using (var stream = File.Open($"database/users.database", FileMode.OpenOrCreate))
            {
                if (stream.Length == 0) return;

                IFormatter formater = new BinaryFormatter();
                _users = (List<User>)formater.Deserialize(stream);

                foreach (var user in _users)
                {
                    user.OnDirty = Update;
                }
            }
        }

        public User[] GetAll()
        {
            return _users.ToArray();
        }

        public User GetById(int id)
        {
            return _users.FirstOrDefault((user) => user.Id == id);
        }

        public User Create()
        {
            int id = 0;
            if (_users.Count > 0)
                id = _users.Max((u) => u.Id) + 1;

            User user = new User(id);
            user.OnDirty = Update;
            _users.Add(user);
            SaveList();

            return user;
        }

        public void Update(User user)
        {
            //
            SaveList();
        }

        public void Delete(User user)
        {
            _users.Remove(user);
            SaveList();
        }

        private void SaveList()
        {
            using (var stream = File.Open($"database/users.database", FileMode.OpenOrCreate))
            {
                IFormatter formater = new BinaryFormatter();
                formater.Serialize(stream, _users);

                stream.Flush();
            }
        }
    }

    delegate void DirtyHandler(User user);

    [Serializable]
    class User
    {
        public int Id { get; private set; }
        private string _name;
        private float _money;

        [NonSerialized]
        public DirtyHandler OnDirty;

        public string Name {
            get => _name;
            set
            {
                _name = value;
                if(OnDirty != null)
                {
                    OnDirty(this);
                }
            }
        }
        public float Money {
            get => _money;
            set
            {
                _money = value;
                if (OnDirty != null)
                {
                    OnDirty(this);
                }
            }
        }

        public User(int id)
        {
            Id = id;
        }
    }
}