单利采用双锁定技术

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

        public static Singleton Instance
        {
            get
            {
                if (instance==null)
                {
                    lock (padlock)
                    {
                        if (instance==null)
                        {
                            instance=new Singleton();
                        }
                    }
                }
                return instance;
            }
        }
    }