.NET 三层（菜鸟的演变）

class Program { static void Main(string[] args) { try { Console.Write("请输入数字A："); string strNumberA = Console.ReadLine(); Console.Write("请选择运算符号(+、-、*、/)："); string strOperate = Console.ReadLine(); Console.Write("请输入数字B："); string strNumberB = Console.ReadLine(); string strResult = ""; strResult = Convert.ToString(Operation.GetResult(Convert.ToDouble(strNumberA),Convert.ToDouble(strNumberB),strOperate)); Console.WriteLine("结果是：" + strResult); Console.ReadLine(); } catch (Exception ex) { Console.WriteLine("您的输入有错：" + ex.Message); } } } public class Operation { public static double GetResult(double numberA,double numberB,string operate) { double result = 0d; switch (operate) { case "+": result = numberA + numberB; break; case "-": result = numberA - numberB; break; case "*": result = numberA * numberB; break; case "/": result = numberA / numberB; break; } return result; } }