C#中的五种单例模式(SIngleton)

1. 写法一(只适用于单线程环境) public sealed class Singleton1 { private Singleton1(){} private static Singleton1 instance = null; public static Singleton1 Instance { get { if(instance == null) instance = new Singleton1(); return instance; } } } 写法一中的代码再多线程中会有问题。若两个线程同时判读instan