Array.cs

using System.Collections.Generic;
using System.Collections;

class Array
{
    public static void Main()
    {
        //System.Console.WriteLine("hello, world");

        Array array = new Array();
        array.Add(3);
        array.Add(5);
        array.Add(7);

        //======================
        foreach(var i in array)
        {
            System.Console.WriteLine(i);
        }
        //======================
        /*
        IEnumrator e = array.GetEnumerator();
        while(e.MoveNext()) 
        {
            System.Console.WriteLine(e.Current);
        }
        */
        //======================
    }
}

class Array : IEnumerable
{
    public int[] values; 
    public int index = 0;

    public Array()
    {
        values = new int[10];
    }

    public void Add(int i) 
    {
        //...
        if(index == values.Length)
        {
            int newValues = new int[values.Length * 2];
            //TODO...
        }
        values[index++] = i;
    }


    public IEnumerator GetEnumerator()
    {
        return new ArrayEnum(this);
    }

    //=================================
    class ArrayEnum : IEnumerator
    {
        int i = -1;
        Array arr;

        public ArrayEnum(Array arr) 
        {
            this.arr = arr;
        }
        public bool MoveNext() 
        { 
            if(i < arr.index - 1) 
            {
                i++; 
                return true;
            }
            else 
            {
                return false;
            }
        }
        public object Current { get { return arr.values[i]; } }

        public void Reset()
        {
            i = -1;
        }
    }
}