如何在特定条件下退出 while 循环以及对无效值的异常处理

Question

这是家庭作业，所以我只是想寻求一些指导。我的代码根据用户给定的索引值 return 数组 [10] 中的一个值。

不起作用的是我需要在输入“99”时停止程序，这个值也会触发 try-catch IndexOutOfRangeException。我无法让程序识别“99”和任何其他超出范围的值之间的区别。我确实用 if-else 尝试过，但是“99”仍然抛出 IndexOutOfRangeException 并且它不会循环。 do-while 的尝试也没有奏效。

代码如下。提前致谢。

using System;
using static System.Console;

class SubscriptExceptionTest
{
static void Main()
{
    double[] array = {20.3, 44.6, 32.5, 46.7, 89.6, 67.5, 12.3, 14.6, 22.1, 13.6};

    int i = 0;

    while (i != 99)
        try
        {

            Write("Enter a number to see the value in that position. Type 99 to stop: ");
            i = Convert.ToInt32(ReadLine());

            double arrayVal = array[i];
            WriteLine("The value at index {0} is {1}", i, arrayVal);
            ReadLine();
        }
        catch (FormatException fe)
        {
            throw new FormatException("You did not enter an integer.");
        }
        catch (IndexOutOfRangeException ie)
        {
            throw new IndexOutOfRangeException("Index was outside the bounds of the array.");
        }
        catch (Exception ex)
        {
            throw new Exception("Error: " + ex.Message);
        }
    }  
}

Answer 1

问题是一旦你捕获了 IndexOutOfRangeException 你又把它扔进了 catch 块中，代码中的任何地方都没有处理。

另一个问题是，在使用它访问导致异常的数组中的 99 之前，您没有检查 i 的值。

见下文 -

int i = 0;

while (i != 99)
    try
                {

                    Write("Enter a number to see the value in that position. Type 99 to stop: ");
                    i = Convert.ToInt32(ReadLine());
                    if(i == 99) {
                      Console.WriteLine("Thanks!!, Breaking here!!!");
                      break;
                    }
                    double arrayVal = array[i];
                    WriteLine("The value at index {0} is {1}", i, arrayVal);
                    ReadLine();
                }

                catch (FormatException fe)
                {
                    throw new FormatException("You did not enter an integer.");
                }

                catch (IndexOutOfRangeException ie)
                {
                    // Show some message here
                }

}

Answer 2

放置一个 if 结构来检查值 99 并在条件为真时退出应用程序。

i = Convert.ToInt32(ReadLine());

if( i == 99 )
{
    //Perform any operation you want to before exiting the application.
    Console.WriteLine("Exiting Application");

    //This will terminate the program.
    Environment.Exit(0);
}

Answer 3

作为规则，Try/Catch 和 异常处理程序应该只在异常情况下使用 。它们是昂贵的。让我向您展示如何使用防御性编程来处理这些问题。

我认为如果任何其他超出范围的值是您想要的答案，则使用Array.Length检查数组边界。

static void Main()
{
double[] array = {20.3, 44.6, 32.5, 46.7, 89.6,67.5, 12.3, 14.6, 22.1, 13.6};

int i = 0;

while (i != 99)
{
        Write("Enter a number to see the value in that position. Type 99 to stop: ");

        var result = ReadLine();

        bool isInteger = int.TryParse(result, out i);

        if (isInteger == false) throw new FormatException("You did not enter an integer.");

        if (i == 99) Environment.Exit(0);

        if (i < 0 || i > array.Length) throw new IndexOutOfRangeException("Index was outside the bounds of the array.");

        double arrayVal = array[i];

        WriteLine("The value at index {0} is {1}", i, arrayVal);

        ReadLine();    
}

如何在特定条件下退出 while 循环以及对无效值的异常处理

How to exit while loop on certain condition and exception handling for invalid values

c#

arrays

while-loop

try-catch

sentinel