使用委托来减少if..else判断

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

namespace _13
{
    public class ClassPeople
    {
        public void SayChinese(string name)
        {
            Console.WriteLine("你好," + name);
        }
        public void SayEnglish(string name)
        {
            Console.WriteLine("Hello," + name);
        }
        public enum Language
        {
            English, Chinese
        }
        public void DoWork(string name, Language lang)
        {
            switch (lang)
            {
                case Language.English:
                    SayEnglish(name);
                    break;
                case Language.Chinese:
                    SayChinese(name);
                    break;
            }
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            ClassPeople cp = new ClassPeople();
            cp.DoWork("李天平", ClassPeople.Language.Chinese);
            cp.DoWork("litianping", ClassPeople.Language.English);
            System.Console.ReadLine();
        }
    }

}

上述代码，根据传进来的语言枚举值和名字符串来输出相应语言的问候语，不过，这个方法的可扩展性太差了，如果以后我们需要再添加韩文版，日文版，就不得不反复修改枚举和Dowork()方法，以适应新的需求。

 

使用委托可以解决优化此类问题。

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

namespace _14
{
    public delegate void SayDelegate(string name);
    public class ClassPeople
    {
        public void SayChinese(string name)
        {
            Console.WriteLine("你好," + name);
        }
        public void SayEnglish(string name)
        {
            Console.WriteLine("Hello," + name);
        }
        //注意此方法，它接受一个SayDelegate类型的方法作为参数
        public void DoWork(string name, SayDelegate MakeSay)
        {
            MakeSay(name);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            ClassPeople cp = new ClassPeople();
            cp.DoWork("李天平", cp.SayChinese);
            cp.DoWork("litianping", cp.SayEnglish);
            System.Console.ReadLine();
        }
    }

}

优化化，我们要加一种问候语，只要新增一个方法就可以了。