用Dictionary应用取代Switch

      对于多个选择支的应用，简单的我们多用If解决，或者应用Switch来做。对于比较复杂的应用，用Switch处理难维护，难扩展。

为了解决这个问题，我们通常可以用设计模式【比如策略模式】来解决。下面的这个解决方式来自CodeProject一个Programmer的解决方案，也可以轻松解决。

using System;
using System.Collections.Generic;

namespace ResharperDemo
{
    class Program
    {
        delegate bool Preperation();

        static void Main(string[] args)
        {
           Program p=new Program();
            p.ShowInfo();
        }

        private void UseSwitchMethod(Food food)
        {
            switch (food)
            {
                case Food.Apple:
                    {
                        PeelApple();
                    }
                    break;
                case Food.AppleJuice:
                    {
                        BakePie();
                    }
                    break;
                default:
                    break;
            }
        }

        private  void ShowInfo()
        {
            Dictionary<Food, Preperation> foodPreperation = new Dictionary<Food, Preperation>();
            foodPreperation.Add(Food.Apple, PeelApple);
            foodPreperation.Add(Food.ApplePie, BakePie);
            foodPreperation.Add(Food.AppleJuice, MakeAppleJuice);
            foodPreperation.Add(Food.Pizza, BakePizza);

            Food food = Food.Apple;
            foodPreperation[food]();
        }

        static bool PeelApple()
        {
            Console.WriteLine("Call PeelApple");
            return true;
        }

        static bool BakePie()
        {
            Console.WriteLine("Call BakePie");
            return true;
        }

        static bool MakeAppleJuice()
        {
            Console.WriteLine("Call MakeAppleJuice");
            return true;
        }

        static bool BakePizza()
        {
            Console.WriteLine("Call BakePizza");
            return true;
        }
    }

    enum Food
    {
        Apple,
        ApplePie,
        AppleJuice,
        Pizza
    }
}