如何在 C# 中读取正则表达式捕获

How to read RegEx Captures in C#(如何在 C# 中读取正则表达式捕获)

问题描述

我开始编写一本 C# 书籍，并决定将 RegEx 加入其中，让枯燥的控制台练习变得更有趣.我想要做的是在控制台中向用户询问他们的电话号码，对照正则表达式进行检查，然后捕获数字，以便我可以按照我想要的方式对其进行格式化.除了 RegEx 捕获部分之外，我已经完成了所有工作.如何将捕获值放入 C# 变量中?

I started a C# book and I decided to throw RegEx's into the mix to make the boring console exercises a little more interesting. What I want to do is ask a user for their phone number in the console, check it against a RegEx, then capture the digits so I can format them the way I want. I've got all that working except the RegEx capture part. How do I get the capture values into C# variables?

还可以随时更正任何代码格式或变量命名问题.

Also feel free to correct any code formatting or variable naming issues.

static void askPhoneNumber()
{
    String pattern = @"[(]?(d{3})[)]?[ -.]?(d{3})[ -.]?(d{4})";

    System.Console.WriteLine("What is your phone number?");
    String phoneNumber = Console.ReadLine();

    while (!Regex.IsMatch(phoneNumber, pattern))
    {
        Console.WriteLine("Bad Input");
        phoneNumber = Console.ReadLine();
    }

    Match match = Regex.Match(phoneNumber, pattern);
    Capture capture = match.Groups.Captures;

    System.Console.WriteLine(capture[1].Value + "-" + capture[2].Value + "-" + capture[3].Value);
}

推荐答案

C# regex API 可能相当混乱.有groups和captures:

The C# regex API can be quite confusing. There are groups and captures:

• 一个group代表一个捕获组，用于从文本中提取子串
• 如果组出现在量词内，则每个组可以有多个捕获.

• A group represents a capturing group, it's used to extract a substring from the text
• There can be several captures per group, if the group appears inside a quantifier.

层次结构是:

• 匹配
  • 集团
    • 拍摄

    (一个匹配可以有多个组，每个组可以有多个捕获)

    (a match can have several groups, and each group can have several captures)

    例如:

    Subject: aabcabbc
    Pattern: ^(?:(a+b+)c)+$
    

    在本例中，只有一组:(a+b+).该组位于量词内，并匹配两次.它生成两个捕获:aab和abb:

    In this example, there is only one group: (a+b+). This group is inside a quantifier, and is matched twice. It generates two captures: aab and abb:

    aabcabbc
    ^^^ ^^^
    Cap1  Cap2
    

    当组不在量词内时，它只会生成一次捕获.在您的情况下，您有 3 个组，每个组捕获一次.您可以使用 match.Groups[1].Value、match.Groups[2].Value 和 match.Groups[3].Value提取您感兴趣的 3 个子字符串，而完全不诉诸 capture 概念.

    When a group is not inside of a quantifier, it generates only one capture. In your case, you have 3 groups, and each group captures once. You can use match.Groups[1].Value, match.Groups[2].Value and match.Groups[3].Value to extract the 3 substrings you're interested in, without resorting to the capture notion at all.

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