单例模式

1、Person类里面

class Person
    {
        private static Person p;
        public static Person GetSingle()
        {
            if (p == null)
            {
                p = new Person();
            }
            return p;
        }
        private Person()
        { }
    }

2、Program类里面

class Program
    {
        static void Main(string[] args)
        {
            Person p = Person.GetSingle();
        }
    }