Question

我正在尝试制作一个程序来确定用户是否是俱乐部会员，然后根据他们的年龄显示他们的折扣金额。我编写了程序，但它给了我一些我无法找到解决方案的错误。我试过搜索这个网站和其他人找到我做错了什么，但每次排除故障都失败了。我是一名学习程序员，所以我确信这是我失踪的原因。对此问题的任何意见将不胜感激。我知道为什么我收到关于当前上下文中不存在的年龄的错误，我只是不明白我的代码中缺少什么，以便正确处理'age'。

这是我的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PA05
{
    class DiscountApp
    {
        public static void Main(string[] args)
        {
            DisplayTitle();
            InputMembershipStatus(age);
            DetermineDiscount(age);
            TerminateProgram();
        }

        public static void DisplayTitle()
        {
            Console.WriteLine("Programming Assignment 5 - Determine Discount\n\tProgrammer: ");
            Console.WriteLine();
            DrawLine();
        }

        public static void InputMembershipStatus(int age)
        {
            Console.WriteLine("Are you a Club Member? <Y or N>: ");
            string aValue = Console.ReadLine();
            if (aValue == "Y" || aValue == "y" || aValue == "Yes" || aValue == "yes")
            {
                age = InputAge();
            }
            else if (aValue == "N" || aValue == "n" || aValue == "No" || aValue == "no")
            {
                Console.WriteLine("Sorry, discounts apply to Club Members only.");
                TerminateProgram();
            }

        }

        public static int InputAge()
        {
            int age;
            Console.Write("Please enter the customer's age: ");
            age = Convert.ToInt32(Console.ReadLine());
            return age;

        }

        public static double DetermineDiscount(int age)
        {
            double discountAmount;
            if (age <= 10 || age >= 60)
            {
                discountAmount = .15;
                Console.WriteLine("The discount is a  {0:P2}", discountAmount);
            }
            else 
            {                
                discountAmount = .1;
                Console.WriteLine("The discount is b {0:P2}", discountAmount);
            }
            return discountAmount;
        }

        public static void DrawLine()
        {
            Console.WriteLine("_________________________________________________________");
        }

        public static void TerminateProgram()
        {
            DrawLine();
            Console.WriteLine("Press any key to terminate the program...");
            Console.ReadKey();
        }
    }
}

Answer 1

问题是c＃中的变量范围有限。您无法像在尝试那样访问在另一个函数中声明的变量。

看起来你正试图在InputMembershipStatus中设置年龄。你想要的是 return 变量：

public static void Main(string[] args)
{
    DisplayTitle();
    // this age variable is declared inside Main 
    // and receives its value from InputMembershipStatus
    int age = InputMembershipStatus();
    DetermineDiscount(age);
    TerminateProgram();
}

和

// this function now returns an int instead of having a parameter
public static int InputMembershipStatus()
{
    int age = 0;
    Console.WriteLine("Are you a Club Member? <Y or N>: ");
    string aValue = Console.ReadLine();
    if (aValue == "Y" || aValue == "y" || aValue == "Yes" || aValue == "yes")
    {
        age = InputAge();
    }
    else if (aValue == "N" || aValue == "n" || aValue == "No" || aValue == "no")
    {
        Console.WriteLine("Sorry, discounts apply to Club Members only.");
        TerminateProgram();
    }

    return age;
}

我会在variable scope和returning values from methods上阅读。

Answer 2

在Main添加：

int age = 22; //initialize it

Answer 3

变量age在调用InputMembershipStatus(age);时第一次使用，因此编译器假定它存在于那里声明为局部变量或全局类级别，但没有声明该变量是本地的或全局的，因此您会收到错误消息。

修复程序的第一件事是更改InputMembershipStatus删除传入的age（不是真的需要）并将请求的值返回给用户。常规值-1用于表示用户未输入正确的年龄值的方式。

    public static int InputMembershipStatus()
    {
        int age = -1;
        Console.WriteLine("Are you a Club Member? <Y or N>: ");
        string aValue = Console.ReadLine();
        if (aValue == "Y" || aValue == "y" || aValue == "Yes" || aValue == "yes")
        {
            age = InputAge();
        }
        else if (aValue == "N" || aValue == "n" || aValue == "No" || aValue == "no")
        {
            Console.WriteLine("Sorry, discounts apply to Club Members only.");
            TerminateProgram();
        }
        return age;
    }

然后您可以修复main函数以获取此值并将其传递给DetermineDiscount

// Ask the age to the user and store it in a local variable here
int age = InputMembershipStatus();

// If we have received a valid value for age, 
// pass that local value to the DetermineDiscount function
if(age != -1)
    DetermineDiscount(age);

TerminateProgram();

最后，InputAge方法需要另一个重要的修复方法。（与你的主要问题无关，但很重要）

   public static int InputAge()
   {
        int age;
        Console.Write("Please enter the customer's age: ");
        if(int.TryParse(Console.ReadLine(), out age))
            return age;
        else
            return -1;

   }

您需要检查用户输入。在非数字输入上使用Convert.ToInt32将使程序崩溃并发生异常（尝试按Enter键而不进行任何输入，空白字符串将具有相同的效果）。相反，Int32.TryParse将尝试将输入转换为有效的整数值，如果成功则将返回true值并在传递的参数中返回转换后的数字。再次返回常规值-1表示无效年龄输入并终止程序

当前上下文中不存在名称“age”

3 个答案: