问题记录

using System;
using System.Collections;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Spectrum spec = new Spectrum();
            foreach (var item in spec)
            {
                item = item + "123";//出错：迭代变量
                Console.WriteLine(item);
            }
        }
    }

    class ColorEnumerator : IEnumerator
    {
        string[] _colors;
        int position = -1;

        public ColorEnumerator(string[] colors)
        {
            _colors = new string[colors.Length];
            for(int i=0;i<_colors.Length;i++)
            {
                _colors[i] = colors[i];
            }
        }

        public object Current
        {
            get
            {
                if (position < 0 || position >= _colors.Length)
                    throw new InvalidOperationException();
                else
                    return _colors[position];
            }
            set//增加写
            {
                if (position < 0 || position >= _colors.Length)
                    throw new InvalidOperationException();
                else
                    _colors[position] = (string)value;
            }
        }

        public bool MoveNext()
        {
            if (position >= _colors.Length-1)
                return false;
            else
            {
                position++;
                return true;
            }
        }

        public void Reset()
        {
            position = -1;
        }
    }

    class Spectrum : IEnumerable
    {
        string[] colors = { "violet", "blue", "cyan", "green", "yellow", "orange", "red" };
        public IEnumerator GetEnumerator()
        {
            return new ColorEnumerator(colors);
        }
    }
}