using System;

​

public class Program

{

    public class User 

    {

        public int Id { get; set; }

        public string Username { get; set; }

    }

​

    // A model that indicates whether a given user is authorized.

    public class UserAuthorization 

    {

        public bool IsAuthorized { get; set; }

        public Guid UserId { get; set; }

    }

​

    public class UserManager

    {

        public IEnumerable<User> GetAuthorizedUsers(IEnumerable<User> users,

            IEnumerable<UserAuthorization> userAuthorizations)

        {

            var filteredUsers = new List<User>();

​

            foreach (var u in users)

            {

                if (userAuthorizations.Count(auth => auth.IsAuthorized) > 0)

                {

                    users.Add(user);

                }

            }

​

            return filteredUsers;

        }

    }

    public static void Main()

    {

        var users = new List<User>() 

        {

            new User() { Id = 1, Username = "abc" },

            new User() { Id = 2, Username = "def" },

            new User() { Id = 3, Username = "ghi" }

        };

        var userAuthorizations = new List<UserAuthorization>() 

        {

            new UserAuthorization() { UserId = 1, IsAuthorized = false },

            new UserAuthorization() { UserId = 2, IsAuthorized = false },

            new UserAuthorization() { UserId = 3, IsAuthorized = true }

        };

        var authorizedUsers = UserManager.GetAuthorizedUsers(users, userAuthorizations);

        foreach (var user in authorizedUsers) 

        {

            Console.WriteLine(string.Format("{1}", user.Username)); 

        }

    }

}

​