c# 設計模式之單例模式（雙if +lock)

public class Singleton
    {
        private static Singleton _Singleton = null;
        private static object Singleton_Lock = new object();
        public static Singleton CreateInstance()
        {
            if (_Singleton == null) //雙if +lock
            {
                lock (Singleton_Lock)
                {
                    Console.WriteLine("路過。");
                    if (_Singleton == null)
                    {
                        Console.WriteLine("被創建。");
                        _Singleton = new Singleton();
                    }
                }
            }
            return _Singleton;
        }
    }