利用Action方法委托重构switch接口

using System;
using System.Collections.Generic;

namespace ConsoleApplication1
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            while (true)
            {
                var s = Console.ReadLine();
                int i;
                int.TryParse(s,out i);

                //swtich分支处理
                switch (i)
                {
                    case 1:
                        MethodHelper.A();
                        break;
                    case 2:
                        MethodHelper.B();
                        break;
                    case 3:
                        MethodHelper.C();
                        break;
                }

                //委托处理
                ActionDic.GetInstance().DoAction(i);
            }
        }
    }

    public class MethodHelper
    {
        public static void A()
        {
            Console.WriteLine("A");
        }
        public static void B()
        {
            Console.WriteLine("B");
        }
        public static void C()
        {
            Console.WriteLine("C");
        }
    }

    public sealed class ActionDic
    {
        private static readonly ActionDic instance = new ActionDic();

        private ActionDic()
        {
            actList = new Dictionary<int, Action>
                          {
                              {1, MethodHelper.A},
                              {2, MethodHelper.B},
                              {3, MethodHelper.C},
                          };
        }
        public static ActionDic GetInstance()
        {
            return instance;
        }
        private readonly Dictionary<int, Action> actList;
      
        public void DoAction(int act)
        {
            Action ar;
            if (actList.TryGetValue(act, out ar))
            {
                ar.Invoke();
            }
        }
    }
}