C# 中的Singleton模式

一般写Singleton基本都是一下这个套路

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class Singleton {     public static Singleton  instance;       private Singleton()     {           }       public static Singleton Getinstance()     {         if(instatnce == null)         {             instance = new Singleton();         }           return instance;     } }

但是今天学到一个C#独有的Singleton写法：

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

这种写法简单实用，大大减少了代码量。

但是缺点就是无法被继承，并且启动时就被初始化，无法延迟初始化。

 

我以这种写法，写了一个简单的LoadBalance类。

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public sealed class LoadBalancer {     public static readonly LoadBalancer balancer = new LoadBalancer();     private ArrayList servers = new ArrayList();     private Random random = new Random();       protected LoadBalancer()     {         servers.Add("SERVER I");         servers.Add("SERVER II");         servers.Add("SERVER III");         servers.Add("SERVER IV");         servers.Add("SERVER V");     }       public string Server     {         get         {             int i = random.Next(servers.Count);             return servers[i].ToString();         }     } }   class Program {     static void Main(string[] args)     {         LoadBalancer b1 = LoadBalancer.balancer;         LoadBalancer b2 = LoadBalancer.balancer;         LoadBalancer b3 = LoadBalancer.balancer;         LoadBalancer b4 = LoadBalancer.balancer;           if (b1 == b2 || b2 == b3 || b3 == b4)             Console.WriteLine("Same instance");         Console.WriteLine(b1.Server);         Console.WriteLine(b2.Server);         Console.WriteLine(b3.Server);         Console.WriteLine(b4.Server);           Console.ReadLine();     } }

调用的结果是：

 

Same instance

SERVER III

SERVER I

SERVER IV

SERVER IV