C#之语法笔记

拓展方法


foreach迭代变量是只读的

枚举器、迭代器

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Spectrum spectra = new Spectrum();
            foreach (var VARIABLE in spectra)
            {
                Console.WriteLine("枚举器：" + VARIABLE);
            }

            MyClass mc = new MyClass();
            foreach (var VARIABLE in mc)
            {
                Console.WriteLine("迭代器：" + VARIABLE);
            }

            //LINQ迭代
            int[] numbers = {2, 5, 6, 7, 2, 12};
            IEnumerable<int> lowNums =
                from number in numbers
                where number < 10
                select number;
            foreach (var VARIABLE in lowNums)
            {
                Console.WriteLine(VARIABLE);
            }

      Console.ReadLine();

        }


    }


    //迭代器实现
    class MyClass {
        public IEnumerator<string> GetEnumerator()
        {
            //IEnumerable myEnumerable = BlockAndWhite();

            return BlockAndWhite();
        }

        public IEnumerator<string> BlockAndWhite()
        {
            yield return "black";
            yield return "gray";
        }
    }
    //枚举器实现
    class Spectrum : IEnumerable
    {
        string[] Colors = {"red", "blue", "yellow"};

        public IEnumerator GetEnumerator()
        {
            return new ColorEnumerator(Colors);
        }
    }

    class ColorEnumerator : IEnumerator
    {
        string[] _colors;
        private 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 bool MoveNext()
        {
            if (_position  < _colors.Length -1)
            {
                _position++;
                return true;
            }
            else
            {
                return false;
            }
        }

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

        public object Current
        {
            get
            {
                if (_position == -1) throw new InvalidOperationException();
                if (_position > _colors.Length) throw new InvalidOperationException();
                return _colors[_position];
            }
        }
    }

}