c# - 在 do...while 中将相关表达式匹配设置为 false

Question

我正在尝试编写一些非常基本的代码，但我也在挑战自己的正则表达式。我已经能够在一定程度上混淆代码，但我真正遇到问题的地方是我试图在表达式为假时运行 do...while 循环。此时我绝对没有收到任何错误，但是 do...while 循环继续运行。

我在下面附上相关代码，希望对您有所帮助。

提前致谢

if (tollResponse == "yes")
{
    Console.WriteLine("How much do you pay per trip?");
    string tollTax = Console.ReadLine();
    Match toll = Regex.Match (tollTax, @"[\d .]+");

    if (toll.Success)
    {
        Math.Round(Convert.ToDecimal(tollTax), 2);
        Console.WriteLine("Good lord that's high... well it's your money");
    }
    else
    {
        do
        {
            Console.WriteLine("Please enter a proper number");
            tollTax = Console.ReadLine();
        }
        while (toll.Success == false);
    }
}

Answer 1

简单的编码错误...添加到您的代码中以解释问题的注释

if (tollResponse == "yes")
{
    Console.WriteLine("How much do you pay per trip?");
    string tollTax = Console.ReadLine();
    //toll.Success gets set here.
    Match toll = Regex.Match(tollTax, @"[\d .]+");

    if (toll.Success)
    {
        //Not sure why you are doing this since you aren't using it in the given code
        Math.Round(Convert.ToDecimal(tollTax), 2);
        Console.WriteLine("Good lord that's high... well it's your money");
    }
    else
    {
        //This is an infinite loop because toll.Success is never set again.
        do
        {
            Console.WriteLine("Please enter a proper number");
            tollTax = Console.ReadLine();
        } while (toll.Success == false);
    }
}

---

我想你想要什么

if (tollResponse == "yes")
{
    Console.WriteLine("How much do you pay per trip?");

    //Loop over the Console.ReadLine() using the else statement and exit if it is right the first time
    do
    {
        string tollTax = Console.ReadLine();
        //toll.Success gets set here.
        Match toll = Regex.Match(tollTax, @"^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*(?:\.[0-9]{2})?$");

        if (toll.Success)
        {
            Console.WriteLine("Good lord that's high... well it's your money");
            //will exit
        }
        else
        {
            Console.WriteLine("Please enter a proper number");
        } 
    } while (toll.Success == false);
}

注意:也删除了 1 行重复代码，更新为使用我推荐的正则表达式并删除了 Math.Round

---

正则表达式工具

[\d .]+

Debuggex Demo

更有效的货币正则表达式

小数可选(两位小数)

^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*(?:\.[0-9]{2})?$

Debuggex Demo

解释:

number (decimal required)

^[+-]?[0-9]{1,3}(?:,?[0-9]{3})*\.[0-9]{2}$

Options: case insensitive

Assert position at the beginning of the string «^»
Match a single character present in the list below «[+-]?»
   Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   The character “+” «+»
   The character “-” «-»
Match a single character in the range between “0” and “9” «[0-9]{1,3}»
   Between one and 3 times, as many times as possible, giving back as needed (greedy) «{1,3}»
Match the regular expression below «(?:,?[0-9]{3})*»
   Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
   Match the character “,” literally «,?»
      Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
   Match a single character in the range between “0” and “9” «[0-9]{3}»
      Exactly 3 times «{3}»
Match the character “.” literally «\.»
Match a single character in the range between “0” and “9” «[0-9]{2}»
   Exactly 2 times «{2}»
Assert position at the end of the string (or before the line break at the end of the string, if any) «$»

将匹配:

1,432.01
456.56
654,246.43
432
321,543
14239729
21379312.32

不会匹配

324,123.432
,,,312,.32
123,.23

取 self 在这里的回答 php - regex - how to extract a number with decimal (dot and comma) from a string (e.g. 1,120.01)?