使用RegEx对字符串进行大写和小写 [英] Use RegEx to uppercase and lowercase the string

问题描述

我正在尝试根据索引将字符串转换为大写和小写.

I am trying to convert a string to uppercase and lowercase based on the index.

我的字符串是一个 LanguageCode ，例如 cc-CC ，其中 cc 是语言代码，而 CC 是国家代码.用户可以以"cC-Cc"之类的任何格式输入.我正在使用正则表达式来匹配数据是否为 cc-CC 格式.

My string is a LanguageCode like cc-CC where cc is the language code and CC is the country code. The user can enter in any format like "cC-Cc". I am using the regular expression to match whether the data is in the format cc-CC.

var regex = new Regex("^[a-z]{2}-[A-Z]{2}$", RegexOptions.IgnoreCase); 
//I can use CultureInfos from .net framework and compare it's valid or not. 
//But the requirement is it should allow invalid language codes also as long 
//The enterd code is cc-CC format

现在，当用户输入 cC-Cc 时，我尝试先将小写的前两个字符小写，然后将大写的后两个字符小写.

Now when the user enters something cC-Cc I'm trying to lowercase the first two characters and then uppercase last two characters.

我可以使用-分割字符串，然后将它们连接起来.

I can split the string using - and then concatenate them.

var languageDetails = languageCode.Split('-');
var languageCodeUpdated = $"{languageDetails[0].ToLowerInvariant()}-{languageDetails[1].ToUpperInvariant()}";

我想我可以避免创建多个字符串，而是使用 RegEx 本身相应地将大小写转换为大写和小写.

I thought can I avoid multiple strings creation and use RegEx itself to uppercase and lowercase accordingly.

在搜索相同内容时，我发现了一些使用 \ L 和 \ U 的解决方案，但是我无法将它们用作 C#编译器显示错误.另外， RegEx.Replace()具有一个我无法理解的参数或委托 MatchEvaluator .

While searching for the same I found some solutions to use \L and \U but I am not able to use them as the C# compiler showing error. Also, RegEx.Replace() has a parameter or delegate MatchEvaluator which I'm not able to understand.

在 C#中有什么方法可以使用 RegEx 将大写字母替换为小写字母，反之亦然.

Is there any way in C# we can use RegEx to replace uppercase with lowercase and vice versa.

推荐答案

.NET regex不支持大小写修改运算符.

.NET regex does not support case modifying operators.

您可以使用 MatchEvaluator :

var result = Regex.Replace(s, @"(?i)^([a-z]{2})-([a-z]{2})$", m => 
    $"{m.Groups[1].Value.ToLower()}-{m.Groups[2].Value.ToUpper()}");

请参见 C#演示.

详细信息

• (?i)- RegexOptions.IgnoreCase mopdiofier
的嵌入式版本
• ^ -字符串的开头
• ([[a-z] {2})-捕获组#1:2个ASCII字母
• --连字符
• ([[a-z] {2})-捕获组2:2个ASCII字母
• $ -字符串的结尾.

• (?i) - the inline version of RegexOptions.IgnoreCase mopdiofier
• ^ - start of the string
• ([a-z]{2}) - Capturing group #1: 2 ASCII letters
• - - a hyphen
• ([a-z]{2}) - Capturing group #2: 2 ASCII letters
• $ - end of string.

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