C# 迭代器

c# 的迭代器模式是通过 IEnumerator 和 IEnumerable 接口来实现的

c# 实现迭代器示例

public class CharList : IEnumerable
    {
        public string TargetStr { get; set; }
        public CharList(string str)
        {
            this.TargetStr = str;
        }

        /// <summary>
        /// 获取迭代器
        /// </summary>
        /// <returns></returns>
        public IEnumerator GetEnumerator()
        {
            return new CharIterator(this.TargetStr);
        }
    }

    /// <summary>
    /// 实现IEnumerator接口
    /// </summary>
    public class CharIterator : IEnumerator
    {
        //引用要遍历的字符串
        public string TargetStr { get; set; }

        //指出当前遍历的位置
        public int position { get; set; }

        public CharIterator(string targetStr)
        {
            this.TargetStr = targetStr;
            this.position = this.TargetStr.Length;
        }

        public object Current
        {
            get
            {
                if (this.position == -1 || this.position == this.TargetStr.Length)
                {
                    throw new InvalidOperationException();
                }
                return this.TargetStr[this.position];
            }
        }

        public bool MoveNext()
        {
            //如果满足继续遍历的条件，设置position的值
            if (this.position != -1)
            {
                this.position--;
            }
            return this.position > -1;
        }

        public void Reset()
        {
            this.position = this.TargetStr.Length;
        }
    }

语法糖模式：

 public class StringList : IEnumerable
    {
        public string[] Count = new string[] { "1", "2", "3" };

        public IEnumerator GetEnumerator()
        {
            for (int i = 0; i < Count.Length; i++)
            {
                yield return Count[i];
            }
        }
    }

调用：

var arr = new StringList();
foreach (string item in arr)
{
   Console.Write(item);
}