delegate

// 可以接受若干参数的委托
    public delegate double Method( params int[] numbers);

    public class Demo
    {

        public double Times( params int[] numbers)
        {
            double result = 1;
            foreach (int i in numbers)
                result *= i;
            return result;
        }

        public double Div(params int[] numbers)
        {
            if (numbers == null || numbers.Length == 0)
                throw new InvalidOperationException("参数错误");
           
            if (numbers.Length == 1)
                return numbers[0];

            double first = numbers[0];
            int length = numbers.Length;

            for (int i = 1; i < length; i++)
            {
                int x = numbers[i];
                if (x == 0)
                    throw new InvalidOperationException("错误的参数");

                first /= x;
            }

            return first;
        }
    }

    public class Calculator
    {

        public Method Times;
        public Method Div;

        public Calculator()
        {
        }

        public double MyTimes(params int[] numbers)
        {
            return this.Times(numbers);
        }

        public double MyDiv(params int[] numbers)
        {
            return this.Div(numbers);
        }

    }

    class Program
    {

        static void Main(string[] args)
        {
            // 装配
            Calculator calculator = new Calculator();

            Demo demo = new Demo();

            calculator.Times = demo.Times;
            calculator.Div = demo.Div;

            // 使用计算器
            double r = calculator.MyTimes(1, 2, 3, 4);
            Console.WriteLine(r);

            double r2 = calculator.MyDiv(12, 2, 3);
            Console.WriteLine(r2);
        }}