如何正确使用do-while循环去

时间：2017-04-28 19:19:32

标签： c#

当我在第一次尝试时运行它可以正常工作，但是当我输入一些垃圾时，它会在给出正确的输入后开始给我错误  “你想买另一种咖啡是或否”。 当我按是，它再次要求我输入

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace Practicing
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                int TotalCoffieCost = 0;
                string UserDecision = string.Empty;
                do
                {
                    int UserChoice = -1;
                    do
                    {
                        Console.ForegroundColor = ConsoleColor.White;
                        Console.WriteLine("Please Enter Your Choice: 1-Small,2-Medium,3-Large");
                        UserChoice = int.Parse(Console.ReadLine());
                        switch (UserChoice)
                        {
                            case 1:
                                TotalCoffieCost += 50;
                                break;
                            case 2:
                                TotalCoffieCost += 70;
                                break;
                            case 3:
                                TotalCoffieCost += 100;
                                break;
                            default:
                                Console.WriteLine("Your choise {0} Is Invalid", UserChoice);
                                break;
                        }
                    } while (UserChoice != 1 && UserChoice != 2 && UserChoice != 3);
                    do
                    {
                        Console.WriteLine("Do You want to buy another coffie Yes or No");
                        UserDecision = Console.ReadLine().ToUpper();
                        if (UserDecision != "YES" && UserDecision != "NO") ;
                        {
                            Console.ForegroundColor = ConsoleColor.Red;
                            Console.WriteLine("Your Choise {0} is invalid ", UserDecision);
                            Console.ForegroundColor = ConsoleColor.White;
                        }
                    } while (UserDecision != "YES " && UserDecision != "NO");
                }
                while (UserDecision.ToUpper() != "NO");
                Console.WriteLine("ThankYou For shopping With Us \n Your Bill Is Genrating Please Wait");
                Thread.Sleep(3000);
                Console.ForegroundColor = ConsoleColor.Magenta;
                Console.WriteLine("Your bill {0}", TotalCoffieCost);
            }
            catch (Exception e)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine(e.Message);
            }
        }

    }
}

4 个答案:

答案 0 :(得分：4)

 } while (UserDecision != "YES " && UserDecision != "NO");

“YES”中有空格。

答案 1 :(得分：1)

您的代码中存在一些拼写错误。

  1. （第50行）是或否问题的while语句等同于"YES "而非"YES"。注意额外的空间。
  2. （第44行）if语句
    3. 后面有一个不需要的分号
  3. 显示总费用后您没有暂停，因此控制台窗口立即关闭。
  4. 您应该允许多个答案为是或否，而不仅仅是"YES"或"NO"。通常也允许y和n。
  5. 消息文本上的大量错别字。

    6. 更新了代码 

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace Practicing
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                int TotalCoffeeCost = 0;
                string UserDecision = string.Empty;
                string[] yesAnswers = new string[] { "YES", "Y" };
                string[] noAnswers = new string[] { "NO", "N" };
                int[] coffeeChoices = new int[] { 1, 2, 3 };

                do
                {
                    int UserChoice = -1;
                    do
                    {
                        Console.ForegroundColor = ConsoleColor.White;
                        Console.WriteLine("Please Enter Your Choice: 1-Small,2-Medium,3-Large");
                        UserChoice = int.Parse(Console.ReadLine());
                        switch (UserChoice)
                        {
                            case 1:
                                TotalCoffeeCost += 50;
                                break;
                            case 2:
                                TotalCoffeeCost += 70;
                                break;
                            case 3:
                                TotalCoffeeCost += 100;
                                break;
                            default:
                                Console.WriteLine("Your choise {0} Is Invalid", UserChoice);
                                break;
                        }
                    } while (!coffeeChoices.Contains(UserChoice));

                    do
                    {
                        Console.WriteLine("Do you want to buy another coffee Yes or No");
                        UserDecision = Console.ReadLine().ToUpper();
                        if (!yesAnswers.Contains(UserDecision) && !noAnswers.Contains(UserDecision))
                        {
                            Console.ForegroundColor = ConsoleColor.Red;
                            Console.WriteLine("Your Choise {0} is invalid ", UserDecision);
                            Console.ForegroundColor = ConsoleColor.White;
                        }
                    } while (!yesAnswers.Contains(UserDecision) && !noAnswers.Contains(UserDecision));
                }
                while (!noAnswers.Contains(UserDecision));

                Console.WriteLine("Thank you For shopping with us \n Your bill is generating. Please wait...");

                Thread.Sleep(3000);

                Console.ForegroundColor = ConsoleColor.Magenta;
                Console.WriteLine("Your bill is {0}", TotalCoffeeCost);

                Console.ForegroundColor = ConsoleColor.White;
                Console.WriteLine("(Press any key to exit)");
                Console.ReadKey();
                Environment.Exit(0);
            }
            catch (Exception e)
            {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine(e.Message);
            }
        }
    }
}

答案 2 :(得分：0)

这里有太多do while个循环。例如：你的开关不需要一个 - 事实上它不应该得到一个。实际上，这整件事可能只想在一个循环中。如果他们想要购买另一个人，你想不断问一个人吗？不。您还谈到了一些您未使用的goto。无论哪种方式 - 这是您需要的帮助：

enum SIZE
{
    SMALL,
    MEDIUM,
    LARGE
}

static void Main(string[] args)
{
     float rTotalCost = 0.0f;
     string sUserDecision = string.Empty;
     do
     {
         SIZE UserChoice;
         Console.ForegroundColor = ConsoleColor.White;
         Console.WriteLine("Please Enter Your Choice: 1-Small, 2-Medium, 3-Large\n");

         UserChoice = (SIZE)int.Parse(Console.ReadLine());
         switch (UserChoice)
         {
              case SIZE.SMALL:
                   rTotalCost += 2.50f;
                   break;
              case SIZE.MEDIUM:
                   rTotalCost += 3.00f;
                   break;
              case SIZE.LARGE:
                   rTotalCost += 3.50f;
                   break;
              default:
                   Console.WriteLine("Your choise {0} Is Invalid", UserChoice);
                   break;
         }

         Console.WriteLine("\n\nDo You want to buy another coffee? Yes or No\n");
         sUserDecision = Console.ReadLine().ToUpper();
         Console.WriteLine("\n");

         if (sUserDecision != "YES" && sUserDecision != "NO")
         {
             Console.ForegroundColor = ConsoleColor.Red;
             Console.WriteLine("\n\nError! Invalid Selection Made! \n\n");
             break;
         }

    } while (sUserDecision != "NO");

    Console.WriteLine("\n\nThank you for shopping!  Your total is:\t$" + rTotalCost);   
    Console.WriteLine("\n\nPress Any key to exit...");


    }
}

不要试图这么努力。它永远不会对你有利。常见错误是过度思考您的问题，从而解决问题。另外，请随意刮开enum同样的工作。

答案 3 :(得分：0)

您还可以通过多种方式简化用户输入的一些处理。首先，您可以围绕第一个输入创建一个硬循环，其中循环约束强制执行1.它是一个整数（使用int.TryParse）和2.它在有效范围内（1 - 3） ：

代码如下所示，我们反复询问一个数字，直到它们给我们有效的输入。 int.TryParse，如果成功，将使用整数填充reponse变量，因此我们也可以在我们的条件下测试它：

int response;
do
{
    Console.Write(" - Enter a number from 1 - 3: ");
} while (!int.TryParse(Console.ReadLine(), out response) 
         || response < 1 || response > 3);

您可以执行的其他优化只是假设Yes|No问题的任何输入都不是以Y开头的No。这可能不是你想要的，但这是一个例子，以防它适合你。基本上，你只需要输入，测试y的第一个字符（忽略大小写），并设置一个布尔结果：

bool buyAnotherOne;

do
{
    // Main code here (omitted) . . .

    buyAnotherOne = Console.ReadLine().StartsWith("y", StringComparison.OrdinalIgnoreCase);
} while (buyAnotherOne);

最后一条建议是在程序结束时暂停，以便用户有机会查看总数。他们等了3秒钟，毕竟... 

// (assume all other program code is above)

Console.Write("\nDone!\nPress any key to exit...");
Console.ReadKey();

最后，它有助于简化代码并使其更具可读性。把它们放在一起看起来像：

int totalCost = 0;
bool buyAnotherOne;

do
{
    Console.ForegroundColor = ConsoleColor.White;
    Console.WriteLine("What size coffee would you like? (1-Small, 2-Medium, 3-Large)?");

    int response;
    do
    {
        Console.Write(" - Enter a number from 1 - 3: ");
    } while (!int.TryParse(Console.ReadLine(), out response)
             || response < 1 || response > 3);

    switch (response)
    {
        case 1:
            totalCost += 50;
            break;
        case 2:
            totalCost += 70;
            break;
        case 3:
            totalCost += 100;
            break;
    }

    Console.Write("Do You want to buy another coffee (yes or no): ");
    buyAnotherOne = Console.ReadLine().StartsWith("y",
        StringComparison.OrdinalIgnoreCase);
} while (buyAnotherOne);

Console.WriteLine("Thank you for shopping with us");
Console.WriteLine("Your bill is genrating; please wait...");
Thread.Sleep(TimeSpan.FromSeconds(3));

Console.ForegroundColor = ConsoleColor.Magenta;
Console.WriteLine("Your total bill: {0}", totalCost);
Console.ForegroundColor = ConsoleColor.White;

Console.Write("\nDone!\nPress any key to exit...");
Console.ReadKey();
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