C#: IEnumerator with Stack Class

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;

namespace Generic_Stack_Implementation
    {
    class Mystack<T> : IEnumerable
        {
        T[] list = null;
        int top;

        public void push(T element)
            {
            top++;
            list[top] = element;

            }

        public Mystack(int size)
            {
            list = new T[size];
            int top = -1;
            }

        public T pop()
            {

            return (list[top--]);
            }

        public IEnumerator GetEnumerator()
            {
            return list.GetEnumerator();
            }
        }

    class Program
        {
        static void Main(string[] args)
            {
            Mystack<int> mys = new Mystack<int>(5);
            mys.push(200);
            mys.push(300);
            mys.push(500);
            Console.WriteLine(mys.pop()); //pop 500
            Console.WriteLine(mys.pop());//pop 300
            IEnumerator ie = mys.GetEnumerator();
            while (ie.MoveNext())
                {
                Console.WriteLine(ie.Current);
                }
            Console.ReadKey();

            }
        }
    }