c# - 年份无法使用正则表达式正确显示

Question

使用正则表达式匹配这行文本我发现年份仍然显示为 2015-01-07 而不仅仅是 2015。谁能看出我的正则表达式有什么问题？

代码行:

    2015-01-07 Wed Jan 07 11:03:43.390 DD Started

我的正则表达式:

    (?<date>(?<year>(?:\d{4}|\d{2})-(?<month>\d{1,2})-(?<day>\d{1,2})))\s(?<logEntry1>.*)\s(?<logEntry2>.*)\s(?<logEntry3>.*)\s(?<time>(?<hour>\d{2}):(?<minutes>\d{2}):(?<seconds>\d{2}).(?<milli>\d{0,3}))\s(?<logEntry>.*)

为什么我不能挑出“年份”？我通过 regex101.com 运行它，这里是捕获组值:

    MATCH 1
    date    [0-10]  `2015-01-07`
    year    [0-10]  `2015-01-07`
    month   [5-7]   `01`
    day [8-10]  `07`
    logEntry1   [11-14] `Wed`
    logEntry2   [15-18] `Jan`
    logEntry3   [19-21] `07`
    time    [22-34] `11:03:43.390`
    hour    [22-24] `11`
    minutes [25-27] `03`
    seconds [28-30] `43`
    milli   [31-34] `390`
    logEntry    [35-45] `DD Started`

Answer 1

您应该将括号从 ))) 移至 (?:\d{4}|\d{2})):

(?<date>(?<year>(?:\d{4}|\d{2}))-(?<month>\d{1,2})-(?<day>\d{1,2}))\s(?<logEntry1>.*)\s(?<logEntry2>.*)\s(?<logEntry3>.*)\s(?<time>(?<hour>\d{2}):(?<minutes>\d{2}):(?<seconds>\d{2}).(?<milli>\d{0,3}))\s(?<logEntry>.*)

实际上，我宁愿对这么长的正则表达式使用 VERBOSE 正则表达式选项，并使用像 # Year 这样的注释来跟踪你的内容:

var rx = new Regex(@"(?<date>
     (?<year>
       (?:\d{4}|\d{2})
     )                  # Year
     -
     (?<month>\d{1,2})
     -
     (?<day>\d{1,2})
   )                    # Date
   \s
   (?<logEntry1>.*)
   \s
   (?<logEntry2>.*)
   \s
   (?<logEntry3>.*)
   \s
   (?<time>
     (?<hour>\d{2})
     :
     (?<minutes>\d{2})
     :
     (?<seconds>\d{2})
     .
     (?<milli>\d{0,3})
   )
   \s
   (?<logEntry>.*)", RegexOptions.IgnorePatternWhitespace);

结果: