public class Persons:IEnumerable
    {
        public Persons(string[] people)
        {
            this.people = people;
        }

        public string[] people { set; get; }
        public IEnumerator GetEnumerator()
        {
            return new PersonEnumable(people);
        }
    }
    public class PersonEnumable : IEnumerator
    {
        public PersonEnumable(string[] people)
        {
            this.people = people;
        }
        private string[] people { set; get; }
        private int index { set; get; } = -1;
        /// <summary>
        /// 当前对象
        /// </summary>
        public object Current {
            get {
                if (index < 0 || index > people.Length-1)
                    return null;
                else
                    return people[index];
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public bool MoveNext()
        {
            if (index < people.Length-1)
            {
                index++;
                return true;
            }
            return false;
        }

        /// <summary>
        /// 
        /// </summary>
        public void Reset()
        {
            index = -1;
        }
    }

var strArr = new string[] { "科比", "詹姆斯", "杜兰特", "诺维茨基", "东契奇", "卢比奥" };
            var persons = new Persons(strArr);
            foreach (var t in persons)
            {
                Console.WriteLine(t);
            }
            //foreachq其实大概就是执行了这段代码，只是不知道是什么时候执行的Reset()
            PersonEnumable personEnumable = new PersonEnumable(strArr);
            while (personEnumable.MoveNext())
            {
                Console.WriteLine(personEnumable.Current);
            }