C# 单例3种写法

public class Singleton
{
private static Singleton _instance = null;
private Singleton(){}
public static Singleton CreateInstance()
{
if(_instance == null)
{
_instance = new Singleton();
}
return _instance;
}
}
第二种考虑了线程安全，不过有点烦，但绝对是正规写法，经典的一叉
public class Singleton
{
private volatile static Singleton _instance = null;
private static readonly object lockHelper = new object();
private Singleton(){}
public static Singleton CreateInstance()
{
if(_instance == null)
{
lock(lockHelper)
{
if(_instance == null)
_instance = new Singleton();
}
}
return _instance;
}
}

第三种可能是C#这样的高级语言特有的，实在懒得出奇
public class Singleton
{
private Singleton(){}
public static readonly Singleton instance = new Singleton();
}
哦，shit！