静态变量

/*声明一个类成员为静态时,意味着无论有多少个类的对象被创建,只会有一个该静态成员的副本
1.所有对象共享

2.不需要声明直接调用
3.类加载时创建
*/


 class Calc
    {
        private Calc()
        {

        }        
        private static double numbera;

        public double NumberA
        {
            get { return numbera; }
            set { numbera = value; }
        }
        private static double numberb;

        public double NumberB
        {
            get { return numberb; }
            set { numberb = value; }
        }

        public static Calc getCalc(double a,double b)
        {
            numbera = a;
            numberb = b;
            return new Calc();
        }


        public double AddFaction()
        {
            return numbera + numberb;
        }

        public double SubFaction()
        {
            return numbera - numberb;
        }
    }

　　

static void Main(string[] args)
        { 
            Calc cl = Calc.getCalc(9.2, 2.1);
            double d1 = cl.AddFaction();
            double d2 = cl.SubFaction();
            Console.WriteLine($"Once---d1:{d1},d2:{d2}");
            cl.NumberA = 3;
            cl.NumberB = 4;
             d1 = cl.AddFaction();
             d2 = cl.SubFaction();
            Console.WriteLine($"Senc---d1:{d1},d2:{d2}");
            Calc cl2 = Calc.getCalc(2, 2);
            Console.WriteLine($"C1A:{cl.NumberA},C1B:{cl.NumberB}");
            Console.WriteLine($"C2A:{cl2.NumberA},C2B:{cl2.NumberB}");
}