public delegate double weituo(double a, double b);
        public static double test1(double a,double b)
        {
            return a * b;
        }
        public static double test2(double a,double b)
        {
            return a / b;
        }
        public static void test3(weituo test)
        {
            Console.WriteLine(test(2.5, 0.5));
        }
        static void Main(string[] args)
        {
            //weituo test;
            //test = test2;
            //test3(test);            
        }