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UserManager.cs

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+using Microsoft.Win32;
+using System;
+using System.Collections.Generic;
+using System.Net.Mail;
+using System.Text;
+
+namespace First_week
+{
+    internal 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}");
+            }
+        }
+    }
+}