Mediator_User_Classes.cs

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// The Mediator pattern acts as a go-between for multiple entities that want
// no knowledge of any of the other entities except at the most abstract
// level.
//
// The classes defined in this module are for handling users.  These classes
// have no knowledge of groups or the mediator class itself.
//
// This is a dead simple implementation of the concept of a user.  There is
// only a name being tracked here.
 
using System;
using System.Collections.Generic;
 
namespace DesignPatternExamples_csharp
{
    public class User
    {
        public User(string name)
        {
            Name = name;
        }
 
 
        public string Name { get; }
 
        public override bool Equals(object? obj)
        {
            if (obj != null)
            {
                if (obj is User)
                {
                    return ((User)obj).Name == Name;
                }
                if (obj is string)
                {
                    return (string)obj == Name;
                }
            }
            return false;
        }
 
 
        public override int GetHashCode()
        {
            return Name.GetHashCode();
        }
    }
 
 
    //########################################################################
    //########################################################################
 
 
    public class UserList
    {
        List<User> _users = new List<User>();
 
        public string[] UserNames
        {
            get
            {
                List<string> userNames = new List<string>();
                foreach (User user in _users)
                {
                    userNames.Add(user.Name);
                }
                userNames.Sort();
                return userNames.ToArray();
            }
        }
 
 
        public User? FindUser(string name)
        {
            return _users.Find(x => x.Equals(new User(name)));
        }
 
 
        public void AddUser(string name)
        {
            if (String.IsNullOrEmpty(name))
            {
                throw new ArgumentNullException("name", "Must specify a user name to add it to the user list.");
            }
 
            User newUser = new User(name);
            if (!_users.Contains(newUser))
            {
                _users.Add(newUser);
            }
        }
 
 
        public void RemoveUser(string name)
        {
            User existingUser = new User(name);
            if (_users.Contains(existingUser))
            {
                _users.Remove(existingUser);
            }
        }
    }
}