c# - 某些文化中的正则表达式和资本 I

Question

在某些文化中大写“I”有什么问题？我发现在某些文化中，在特殊条件下无法找到 - 如果您正在寻找带有标志 RegexOptions.IgnoreCase 的 [a-z]。这是示例代码:

var allCultures = CultureInfo.GetCultures(CultureTypes.AllCultures);
var allLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var allLettersCount = allLetters.Length;

foreach (var culture in allCultures)
{
    Thread.CurrentThread.CurrentCulture = culture;
    Thread.CurrentThread.CurrentUICulture = culture;

    var matched = string.Empty;
    foreach (var m in Regex.Matches(allLetters, "[A-Za-z0-9]", RegexOptions.IgnoreCase))
        matched += m;

    var count = matched.Length;
    if (count != allLettersCount)
        Console.WriteLine("Culture '{0}' - {1} missing; Matched: {2}", culture.Name, (allLettersCount - count).ToString(), matched);
}

输出是(注意每一行都缺少大写字母 I):

Culture 'az' - 1 missing; Matched:          ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'az-Cyrl' - 1 missing; Matched:     ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'az-Cyrl-AZ' - 1 missing; Matched:  ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'az-Latn' - 1 missing; Matched:     ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'az-Latn-AZ' - 1 missing; Matched:  ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'tr' - 1 missing; Matched:          ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Culture 'tr-TR' - 1 missing; Matched:       ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789

有趣的是，如果不使用标志“IgnoreCase”，那么它工作正常，并找到“I”。

Answer 1

答案在Wikipedia中:

The casing of the dotless and dotted I forms differ from other languages. That implies that a case insensitive matching expected by an English person doesn't match the expectations of a Turkish user. The "Turkish I" is often used as an example of the problems with case insensitivity in computing.

另一种解释可以在 MSDN 上找到: