创建一个简单的迭代器

在C# 1.0中，自己写代码实现IEnumerator

  class IterateCollection : IEnumerable
    {
        private string[] strarr = new string[5];
        public IterateCollection() { }
        public IterateCollection(string[] strarr)
        {
            this.strarr = strarr;
        }
        public string this[int index]
        {
            get { return strarr[index]; }
        }

        public int Count
        {
            get { return strarr.Length; }
        }

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

class IterateEnumertor : IEnumerator
    {
        private readonly IterateCollection collection;
        private int index;
        private object current;
        public IterateEnumertor(IterateCollection collection) 
        {
            this.collection = collection;
            index = 0;
        }

        public object Current
        {

            get { return current; }
        }

        public bool MoveNext()
        {
            if (index + 1 > collection.Count) { return false; }
            else 
            {
                this.current = collection[index];
                index++;
                return true;
            }
        }

        public void Reset()
        {
            index = 0;    
        }
    }

  static void Main(string[] args)
        {
            string[] strarr = { "刘诗诗","陈乔恩","刘亦菲"};
            IterateCollection collection = new IterateCollection(strarr);
            foreach(string str in collection)
            {
                Console.WriteLine(str.ToString());
            }
            Console.Read();
        }

摘要：1 想要可以被迭代，就要实现IEnumerable,或者IEnumerable<T>,并且重写GetEnumerator()；方法，得到一个迭代器

     2 在C#1.0中迭代器要自己写，通过实现IEnumerator,或者IEnumerator<T>,并且重写MoveNext();和Reset();方法

C#2.0简化了迭代器的实现

   

       public IEnumerator GetEnumerator()
        {
            //return new IterateEnumertor(this);
            for (int index = 0; index < strarr.Length; index++) 
            {
                yield return strarr[index];
            }
        }

摘要 yield return 关键字告诉编译器去执行实现过程，我们程序员就减少了编码量