C#自建类实现集合接口IEnumerable, IEnumerator

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

namespace MyConProject
{

    /// <summary>
    /// C#自建集合类MyArrayList实现集合接口IEnumerable, IEnumerator
    /// 实现方法 inr add(object value)，void Remove(object o)， int Count, void Clear
    /// </summary>
    class MyArrayList : IEnumerable, IEnumerator
    {
        private object[] obj;  //初始化保存集合元素的object数组
        private int count = 0; //初始化数组个数0     
        private int index = -1;//初始化数组下标为-1，避免一开始下标移动出错
        /// <summary>
        /// 返回集合内元素的总个数
        /// </summary>
        public int Count
        {
            get { return count; }
        }
        /// <summary>
        /// 无参构造，初始化数组个数0 
        /// </summary>
        public MyArrayList()

        {
            obj = new object[count];
        }
        /// <summary>
        /// 有参构造，指定初始化数组个数 
        /// </summary>
        /// <param name="index"></param>
        public MyArrayList(int index)
        {
            obj = new object[index];
        }

        /// <summary>
        /// 新增功能，添加到数组末尾处，返回数组下标
        /// </summary>
        /// <param name="obj">要新增的对象</param>
        /// <returns></returns>
        public int add(object o)
        {
            object[] old = obj;
            if (count >= obj.Length)
            {
                obj = new object[old.Length + 1];
                for (int i = 0; i < old.Length; i++)
                {
                    obj[i] = old[i];
                }
            }
            obj[count] = o;
            count++;