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。