using System;

using System.Collections;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var rdv = new RollingValues<int>(20);

        var r = new Random();

        for (var i = 0; i < 50; i++)

        {

            rdv.SetValue(r.Next(0,100));

            Console.WriteLine("ValueSet: {0}", string.Join(",", rdv));

        }

    }

​

    internal class RollingValues<T> : IEnumerable<T>

    {

        private T[] _items;

        private int _currentIndex = 0;

        private int _count = 0;

        public RollingValues(int capacity)

        {

            _items = new T[capacity];

        }

​

        public T this[int index] { get => _items[(index + _currentIndex) % Count]; }

​

        public int Count => _count;

        public bool IsReadOnly => false;

​

        public void SetValue(T value)

        {

            if (_count < _items.Length)

            {

                _items[_currentIndex++] = value;

                if (_currentIndex >= _items.Length)

                    _currentIndex = 0;

                _count++;

            }

            else

            {

                _items[_currentIndex++] = value;

                if (_currentIndex >= _items.Length)

                    _currentIndex = 0;

            }

        }

​

        public int GetHashCode(IEqualityComparer comparer)

        {

            // Simplified version for demonstration

            return comparer.GetHashCode(_items);

        }

​

        public IEnumerator<T> GetEnumerator()

        {

            for (int i = 0; i < _count; i++)

            {

                yield return this[i];

            }

        }

​

        IEnumerator IEnumerable.GetEnumerator()

        {

            return GetEnumerator();

        }

    }

}