UtilityLibrary/UserManager.cs

using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.Net.Mail;
using System.Text;

namespace First_week
{
    public class UserManager
    {
        public List <User> Registory = new();

        public void AddUser(User user)
        {
            CheckUniqe(user);
            Registory.Add(user); 
        }

        public void RemoveUser(Guid id)
        {
            User? user = Registory.Find(x => x.Id == id);
            if (user == null)
                return;

            Registory.Remove(user);
        }

        public User Find(Guid id)
        {
            User? user = Registory.Find(x => x.Id == id);
            if (user == null)
                throw new Exception("Not found");   

            return user;
        }

        public User Find(MailAddress email)
        {
            User? user = Registory.Find(x => x.Email == email);
            if (user == null)
                throw new Exception("Not found");

            return user;
        }

        private void CheckUniqe(User user)
        {
            if (Registory.FirstOrDefault(x => x.Equals(user)) != null)
                throw new Exception("Such a user already exists");
        }

        public void Show()
        {
            foreach (var user in Registory)
            {
                Console.WriteLine($"{user.GetFullName} {user.Id}");
            }
        }
    }
}