用户输入无效后程序结束

Question

如何使程序状态为用户输入无效，然后在按下回车后关闭？我有第一个错误，指出用户输入的值是错误的，再试一次，但如果用户输入 same/invalid 数字，它将重复最后一件事。我怎样才能让它限制再尝试一次，然后如果用户没有提供有效的输入，它就会正确和错误？代码如下：

        string First;
        string Last;
        First = "Cristiano";
        Last = " Ronaldo";
        Console.Write("Please enter student name <First Last>: ");
        Console.WriteLine(First + Last);

        Console.WriteLine(" ");

        Console.WriteLine("*************NOTE**********************************************");
        Console.WriteLine("*** Be sure to include decimal point for scores.            ***");
        Console.WriteLine("***     !!!All score should range from 0.00 to 100.00 !!    ***");
        Console.WriteLine("***                                                         ***");
        Console.WriteLine("*** For example : 80.50                                     ***");
        Console.WriteLine("***************************************************************");

        Console.WriteLine(" ");

        double Exam_1 = -1;
        double Exam_2;
        double Exam_3;
        double Assignment_1;
        double Assignment_2;

        Console.Write("Please enter score for Exam 1 <Example: 100.0>: ");
        Exam_1 = Convert.ToDouble(Console.ReadLine());

        while (Exam_1 < 0.0 || Exam_1 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0. or greater than 100.0. Please re-enter the score for Exam 1 <Example: 95.0>:");
            Exam_1 = Convert.ToDouble(Console.ReadLine());
        }

        Console.Write("Please enter score for Exam 2 <Example: 0.0>: ");
        Exam_2 = Convert.ToDouble(Console.ReadLine());

        while (Exam_2 < 0.0 || Exam_2 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 2 <Example: 95.0>:");
            Exam_2 = Convert.ToDouble(Console.ReadLine());
        }

        Console.Write("Please enter score for Exam 3 <Example: 60.8>: ");
        Exam_3 = Convert.ToDouble(Console.ReadLine());

        while (Exam_3 < 0.0 || Exam_3 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 3 <Example: 95.0>:");
            Exam_3 = Convert.ToDouble(Console.ReadLine());
        }

        Console.WriteLine(" ");

        Console.Write("Please enter score for Assignment 1 <Example: 100.0>: ");
        Assignment_1 = Convert.ToDouble(Console.ReadLine());

        while (Assignment_1 < 0.0 || Exam_2 > 100.0)
        {
            Console.Write("Assignment score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 1 <Example: 95.0>:");
            Assignment_1 = Convert.ToDouble(Console.ReadLine());
        }

        Console.Write("Please enter score for Assignment 2 <Example: 23.46>: ");
        Assignment_2 = Convert.ToDouble(Console.ReadLine());

        while (Assignment_2 < 0.0 || Assignment_2 > 100.0)
        {
            Console.Write("Assignment score can not be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 2 <Example: 56.0>: ");
            Assignment_2 = Convert.ToDouble(Console.ReadLine());
        }

        Console.WriteLine(" ");

        Console.WriteLine(" -------------- OUTPUT ---------------");

        Console.WriteLine(" ");

        Console.Write("Student: ");
        Console.WriteLine(First + Last);

        Console.WriteLine(" ");



















        Console.Write("Press any key to continue . . . ");
        Console.ReadLine();
    }
}

}

Answer 1

鉴于这是一项作业，我不确定您的教授是否像我的教授一样，我们只能使用我们在 class 中学到的知识。也就是说，您可能想查看 double.tryparse https://msdn.microsoft.com/en-us/library/994c0zb1(v=vs.110).aspx

如果输入可解析为双精度值，则函数将 return 返回布尔值；如果输入无效，则返回 false。上面 MSDN 链接上的代码示例应该会给您一个良好的开端。

Answer 2

试试这个代码

    static void Main(string[] args)
    {
        string First;
        string Last;
        First = "Cristiano";
        Last = " Ronaldo";
        Console.Write("Please enter student name <First Last>: ");
        Console.WriteLine(First + Last);

        Console.WriteLine(" ");

        Console.WriteLine("*************NOTE**********************************************");
        Console.WriteLine("*** Be sure to include decimal point for scores.            ***");
        Console.WriteLine("***     !!!All score should range from 0.00 to 100.00 !!    ***");
        Console.WriteLine("***                                                         ***");
        Console.WriteLine("*** For example : 80.50                                     ***");
        Console.WriteLine("***************************************************************");

        Console.WriteLine(" ");

        double Exam_1 = -1;
        double Exam_2;
        double Exam_3;
        double Assignment_1;
        double Assignment_2;

        Console.Write("Please enter score for Exam 1 <Example: 100.0>: ");
        Exam_1 = Convert.ToDouble(Console.ReadLine());
        var exitProgram = false;
        var errorCount = 0;

        while (Exam_1 < 0.0 || Exam_1 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0. or greater than 100.0. Please re-enter the score for Exam 1 <Example: 95.0>:");
            Exam_1 = Convert.ToDouble(Console.ReadLine());
            ++errorCount;
            ErrorCount(errorCount);
        }

        Console.Write("Please enter score for Exam 2 <Example: 0.0>: ");
        Exam_2 = Convert.ToDouble(Console.ReadLine());
        errorCount = 0;
        while (Exam_2 < 0.0 || Exam_2 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 2 <Example: 95.0>:");
            Exam_2 = Convert.ToDouble(Console.ReadLine());
            ++errorCount;
            ErrorCount(errorCount);
        }

        Console.Write("Please enter score for Exam 3 <Example: 60.8>: ");
        Exam_3 = Convert.ToDouble(Console.ReadLine());
        errorCount = 0;
        while (Exam_3 < 0.0 || Exam_3 > 100.0)
        {
            Console.Write("Exam score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Exam 3 <Example: 95.0>:");
            Exam_3 = Convert.ToDouble(Console.ReadLine());
            ++errorCount;
            ErrorCount(errorCount);
        }

        Console.WriteLine(" ");

        Console.Write("Please enter score for Assignment 1 <Example: 100.0>: ");
        Assignment_1 = Convert.ToDouble(Console.ReadLine());
        errorCount = 0;
        while (Assignment_1 < 0.0 || Exam_2 > 100.0)
        {
            Console.Write("Assignment score cannot be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 1 <Example: 95.0>:");
            Assignment_1 = Convert.ToDouble(Console.ReadLine());
            ++errorCount;
            ErrorCount(errorCount);
        }

        Console.Write("Please enter score for Assignment 2 <Example: 23.46>: ");
        Assignment_2 = Convert.ToDouble(Console.ReadLine());
        errorCount = 0;
        while (Assignment_2 < 0.0 || Assignment_2 > 100.0)
        {
            Console.Write("Assignment score can not be less than 0.0 or greater than 100.0. Please re-enter the score for Assignment 2 <Example: 56.0>: ");
            Assignment_2 = Convert.ToDouble(Console.ReadLine());
            ++errorCount;
            ErrorCount(errorCount);
        }

        Console.WriteLine(" ");

        Console.WriteLine(" -------------- OUTPUT ---------------");

        Console.WriteLine(" ");

        Console.Write("Student: ");
        Console.WriteLine(First + Last);

        Console.WriteLine(" ");
        Console.Write("Press any key to continue . . . ");
        Console.ReadLine();
    }

    public static void ErrorCount(int errorCount)
    {
        if (errorCount > 0)
        {
            Console.Write("Error count too much ! . . . ");
            Console.Write("Press any key to exit . . . ");
            Console.ReadKey();
            Environment.Exit(0);
        }

    }

请记住，它不会检测用户输入的是字母数字还是特殊字符，但您明白了。

Answer 3

您显然是编码世界的新手，这看起来像是一道家庭作业题。但是，我怀疑您突出显示的问题的根源在于，当您调用无法转换输入的 Convert.ToDouble(Console.ReadLine()) 时会抛出异常，而您没有捕捉到它。

您可以在此处阅读有关异常的更多信息：https://msdn.microsoft.com/en-us/library/ms173160.aspx

要解决这个问题，我会执行如下操作：

Console.Write("Please enter score for Exam 1 <Example: 100.0>: ");
while(!Double.TryParse(Console.ReadLine(), out Exam_1))
{
      Console.Write("Try again...");
}

Answer 4

看看你的代码逻辑。 while 循环将不断循环，直到表达式的计算结果为 false。如果您希望提前终止循环，则需要通过更改条件表达式、使用不同类型的循环或使用 break 语句来修改循环。

Here is some reference material from Microsoft's website.

想一想您的问题并问问自己：如果您手动执行此操作，您将如何执行此操作？如果你处在计算机的位置，你会采取什么逻辑步骤？您会做出什么决定以及做出这些决定需要哪些信息？

用户输入无效后程序结束

Program ends after user input is invalid

c#

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