置若惘闻

delegate double ProcessDelegate(double param1, double param2);
 
        static double Multiply(double param1, double param2)
        {
            return param1 * param2; //返回乘积
        }
 
        static double Divide(double param1, double param2)
        {
            return param1 / param2; //两数相除
        }
 
 
        static void Main(string[] args)
        {
            ProcessDelegate process;
            Console.WriteLine("Enter 2 numbers separated with a comma:"); //输入两个数字并且以逗号隔开
            string input = Console.ReadLine();
            int commaPos = input.IndexOf(',');//indexof:查找第一次出现逗号的位置;indexof(','2)第二次出现逗号的位置;indexof(',',3,2)从第三开始查，查两位；返回值是绝对位置，为空则为 -1
            double param1 = Convert.ToDouble(input.Substring(0, commaPos));//Substring：截取从0-commaPos（2）的字符串
            double param2 = Convert.ToDouble(input.Substring(commaPos + 1, input.Length - commaPos - 1));
            Console.WriteLine("Enter M to Multiply or D to divide:");
            input = Console.ReadLine();
            if (input == "M")
                process = new ProcessDelegate(Multiply);
            else
                process = new ProcessDelegate(Divide);
            Console.WriteLine("Result: {0}", process(param1, param2));
            Console.ReadKey();
            }