class Program
    {
        static void Main(string[] args)
        {
            TasksList tl = new TasksList(new int[] { 1, 2, 3, 4, 5 });
            Console.WriteLine("The tasks list length " + tl.Tasks.Length);
        }
    }

    class Task
    {
        private readonly TasksList list;
        private readonly int id;

        public Task(TasksList list, int id)
        {
            this.list = list;
            this.id = id;
        }
    }

    class TasksList
    {
        private readonly Task[] tasks;

        public TasksList(int[] ids)
        {
            var mutableList = new List<Task>();
            foreach (int id in ids)
            {
                Task t = new Task(this, id);
                mutableList.Add(t);
            }

            this.tasks = mutableList.ToArray();
        }

        public Task[] Tasks { get { return tasks; } }
    }