关于在 C# 中执行 while 循环的问题

Question

所以我有这个代码，您可以在其中输入“区号”，然后输入您希望通话时长。这基本上是一个简单的计算器，可以根据您的区号计算通话费用。如果我输入了无效的区号，我很难弄清楚如何保持循环运行。到目前为止，如果我输入了无效的区号，整个程序只会在命令提示符下结束。代码如下：

using System;
using static System.Console;

namespace Chapter6._1
{
    class Program
    {
        static void Main()
        {
            // array info //
            int[] phoneAreacode = { 608, 414, 262, 815, 715, 920 };
            double[] phoneCost = { .05, .10, .07, .24, .16, .14 };
            // declaring variables //
            int x;
            int areaCode;
            double cost = 0;
            int callLength;
            bool validAreacode = false;
            // start of actual code //
            Write("Enter in the area code you want to call: ");
            areaCode = Convert.ToInt32(ReadLine());
            x = 0;
            while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
                ++x;
            if(x != phoneAreacode.Length)
            {
                validAreacode = true;
                cost = phoneCost[x];
            }
            if (validAreacode)
            {
                Write("Enter in the length of your call: ");
                callLength = Convert.ToInt32(ReadLine());
                double finalCost = callLength * cost;
                WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));
            }
            else
            {
                WriteLine("YOU MUST ENTER A VALID AREA CODE!");
            }
        }
    }
}

Answer 1

您可以将 Read 和 Check 例程包装到另一个 while 循环中：

bool validAreacode = false;

while(!validAreacode)
{
    // start of actual code //
    Write("Enter in the area code you want to call: ");
    areaCode = Convert.ToInt32(ReadLine());
    x = 0;
    while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
        ++x;
    if(x != phoneAreacode.Length)
    {
        validAreacode = true;
        cost = phoneCost[x];
    }
    else
    {
        WriteLine("YOU MUST ENTER A VALID AREA CODE!");
    }
}

这对您来说是最简单的解决方案（不需要对您的代码进行太多更改）。但是您的代码仍然存在问题。如果用户尝试打印任何非数字字符而不是区号，您的程序将崩溃。

Answer 2

您可以在此处发送do-While：

基本上，当您执行do-while 时，您会强制执行do 上的代码，直到完成while 中的条件。在您的情况下，您需要在 do 语句中添加对 pohne 编号的检查，并且要知道该人是否选择了正确的值，您可以执行 Array.FindIndex()： 这将是您的do-while 循环，我也将您的x 更改为index 尝试使用具有某些含义的变量的名称。 （无论如何索引并不完美）

do
{
    Write("Enter in the area code you want to call: ");
    areaCode = Convert.ToInt32(ReadLine());

    index = Array.FindIndex(phoneAreacode, w => w == areaCode);
    if (index >= 0)
    {
        validAreacode = true;
    }
    else
    {
        WriteLine("YOU MUST ENTER A VALID AREA CODE!");
    }

} while (!validAreacode);

这将是你的整个主要方法：

int[] phoneAreacode = { 608, 414, 262, 815, 715, 920 };
double[] phoneCost = { .05, .10, .07, .24, .16, .14 };
// declaring variables //
int index;
int areaCode;
int callLength;
bool validAreacode = false;
// start of actual code //



do
{
    Write("Enter in the area code you want to call: ");
    areaCode = Convert.ToInt32(ReadLine());

    index = Array.FindIndex(phoneAreacode, w => w == areaCode);
    if (index >= 0)
    {
        validAreacode = true;
    }
    else
    {
        WriteLine("YOU MUST ENTER A VALID AREA CODE!");
    }

} while (!validAreacode);


Write("Enter in the length of your call: ");
callLength = Convert.ToInt32(ReadLine());
double finalCost = callLength * phoneCost[index];
WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));

如您所见，您还可以删除 while 您必须循环数组和 if-else 以获得有效代码。假设当代码到达该点时，该区域是正确的。

最好尝试删除if-else 的号码。

Answer 3

你可能需要循环整个代码部分，像这样

while (true)
{

  Write("Enter in the area code you want to call: ");

  var input = ReadLine();

  if (input == "Exit")
      break;

  areaCode = Convert.ToInt32(input);
  x = 0;

while (x < phoneAreacode.Length && areaCode != phoneAreacode[x])
       ++x;      

  if(x != phoneAreacode.Length)
  {
       validAreacode = true;
        cost = phoneCost[x];
   }
  else if (validAreacode)
  {
      Write("Enter in the length of your call: ");
      callLength = Convert.ToInt32(ReadLine());
      double finalCost = callLength * cost;
      WriteLine("Your call to area code " + areaCode + " for " + callLength + " minutes will cost " + finalCost.ToString("C"));
  }
  else
  {
      WriteLine("YOU MUST ENTER A VALID AREA CODE!");
   }

}

不要忘记在用户输入非数字内容时添加检查