C graphical tutorial (Fourth Edition)_ Chapter 18 enumerator and iterator: enumerator samplep340

using System;
using System.Collections;


namespace Chapter18EnumeratorSampleP340
{
    class ColorEnumerator:IEnumerator
    {
        string[] _colors;
        int _position = -1;

        public ColorEnumerator(string[] theColors)//  Constructors 
        {
            _colors = new string[theColors.Length];
            for (int i=0;i<theColors.Length;i++)
                _colors[i] = theColors[i];
        }
        public object Current// Realization Current  Get the value of the element at the current position in the collection 
        {
            get
            {
                if (_position == -1)
                    throw new InvalidOperationException();
                if (_position >= _colors.Length)
                    throw new InvalidOperationException();

                return _colors[_position];
            }
        }
       public bool MoveNext()// Realization MoveNext()： Let the iterator move on to the next element , Successfully returns true, conversely   return false
        {
            if (_position < _colors.Length - 1)
            {
                _position++;
                return true;
            }
            else
                return false;
        }
        public void Reset()// Realization Reset： Set the enumerator to return to its original position , Before the first element 
        {
            _position = -1;
        }


    }
    class Spectrum :IEnumerable// Interface System.Collections.IEnumerator, It is exposed that an enumerator supports simple iterations ,
                               // In a non generic set . You have to implement functions GetEnumerator()
    {
        string[] Colors = { "violet", "blue", "cyan", "green", "yellow", "orange", "red" };

        public IEnumerator GetEnumerator()
        {
            return new ColorEnumerator(Colors);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Spectrum spectrum = new Spectrum();
            foreach (string color in spectrum)
                Console.WriteLine(color);
            Console.WriteLine("Hello World!");
        }
    }
}