RegEx强制量词有效

Question

我正在努力让名字首字母的正则表达式验证起作用。

我有以下代码：

// S.P. of Sp.A. 
string voorletters = "S.P.aAa"; // This should be invalid
string regexPattern = "^([A-Z]{1}[.]|[A-Z]{1}[a-z]{1,}[.])*";
var isMatch = Regex.IsMatch(voorletters, regexPattern);

以下示例应该无效，但确实匹配，因此会通过。 http://regexhero.net/tester/?id=439e7c6e-ce74-4b5a-ac60-d8abeee69675

如何强制量词（*）进行验证？

Answer 1

试试这个：

^([A-Z][a-z]?\.)*$

Debuggex Demo

Answer 2

尝试这种模式：

"^([A-Z]{1}[.]|[A-Z]{1}[a-z]{1,}[.]??)*$"

最后的$是必需的，因为在你的用例中，匹配的部分实际上只是“S.P.”。 “??”在第二个点后面是可选的，取决于你在实践中想要什么 - 应该“S.P.Aa”工作与否？

Answer 3

尝试使用：

^([A-Z][a-z]*\.)+$

<强>解释

The regular expression:

(?-imsx:^([A-Z][a-z]*\.)+$)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (                        group and capture to \1 (1 or more times
                           (matching the most amount possible)):
----------------------------------------------------------------------
    [A-Z]                    any character of: 'A' to 'Z'
----------------------------------------------------------------------
    [a-z]*                   any character of: 'a' to 'z' (0 or more
                             times (matching the most amount
                             possible))
----------------------------------------------------------------------
    \.                       '.'
----------------------------------------------------------------------
  )+                       end of \1 (NOTE: because you are using a
                           quantifier on this capture, only the LAST
                           repetition of the captured pattern will be
                           stored in \1)
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------