C# if判断问题

Question

using System;
using System.Collections.Generic;
using System.Text;namespace ConsoleApplication1
{
    class ch0105
    {
        static void Main(string[] args)
        {
            string isVip;
            int money;            Console.WriteLine("您是会员吗？(y/n)");
            isVip = Console.ReadLine();
            Console.WriteLine("请输入您的购书金额");
            money = int.Parse(Console.ReadLine());            if (isVip=="Y"|| isVip=="y")
            {
                if (money >= 200)
                {
                    Console.WriteLine("可以打折，打折后金额为{0}", money * 0.75);
                }
                else if (money >= 100 && money < 200)
                {
                    Console.WriteLine("可以打折，打折后金额为{0}", money * 0.75);
                }
                else
                {
                    Console.WriteLine("输入错误");
                }
            }
            else if (isVip == "n" || isVip == "N")
            {
                if (money >= 100)
                {
                    Console.WriteLine("可以打折,金额为{0}", money * 0.9);
                }
                else
                {
                    Console.WriteLine("不能打折，金额为{0}", money);
                }
            }
            else
            {
                Console.WriteLine("输入错误");
            }
           
            Console.ReadLine();
        }
    }
}
以上代码 在执行isVip 判断时，如输入P 则带程序最后显示输入错误。
如何修改才能在输入不用执行所有的if判断 提示输入错误

Answer 1

最简单的方法，可以在外面加一个try catch来捕获异常，在异常里提示输入错误

Answer 2

修改程序结构：Console.WriteLine("请输入您的购书金额");
money = int.Parse(Console.ReadLine());挪到if里。

Answer 3

static void Main(string[] args)
{
            string isVip;
            int money;            Console.WriteLine("您是会员吗？(y/n)");
            isVip = Console.ReadLine().ToLower();            if ("yn".Contains(isVip))
            {
                Console.WriteLine("输入错误");
                return;               
            }

            Console.WriteLine("请输入您的购书金额");
            money = int.Parse(Console.ReadLine());            if (isVip=="y")
            {
                if (money >= 200)
                {
                    Console.WriteLine("可以打折，打折后金额为{0}", money * 0.75);
                }
                else if (money >= 100 && money < 200)
                {
                    Console.WriteLine("可以打折，打折后金额为{0}", money * 0.75);
                }
                else
                {
                    Console.WriteLine("输入错误");
                }
            }
            else
            {
                if (money >= 100)
                {
                    Console.WriteLine("可以打折,金额为{0}", money * 0.9);
                }
                else
                {
                    Console.WriteLine("不能打折，金额为{0}", money);
                }
            }  
            //最后的判断全删掉         
            Console.ReadLine();
        }
    }

Answer 4

if ("yn".Contains(isVip))修改：if (isVip != "y" && isVip != "n")