c# - 日期格式 dd.MM.yyyy 的正则表达式模式

Question

是否有任何正则表达式模式存储，我可以找到像 dd.MM.yyyy 这样的模式，或者你可以帮助我吗？

我正在使用带有数据注释的数据验证：

[RegularExpression(@"pattern", ErrorMessage = "incorrect date format")]
public string MyDate { get; set; }

Answer 1

根据 ECMAScript 规范，一个快速的答案可能是

^(\d{2}).\d{2}.(\d{4})$

Answer 2

您可以随时尝试使用正则表达式工具，例如“RegExBuddy”或“Rad Software Regular Expression Designer”。

但是你想要的正则表达式可能是这样的：

\d{2}.\d{2}.\d{4}?

Answer 3

你可以使用这样的东西：

\d{1,2}\\.\d{1,2}\\.(19\d\d|20\d\d)

Answer 4

不检查短月和闰年的模式：

string pattern = @"(0[1-9]|[12][0-9]|3[01])\.(0[1-9]|1[012])\.(19|20)\d\d"

Answer 5

// Each month has a different number of days.
// More over, we have different number of days in February which depends on whether
// the year is a leap year. Here is how to solve this problem:
// 1) if the first digit is even, the second digit must be 0, 4, or 8
// 2) if the first digit is odd, the second digit must be 2 or 6
var pattern = "^([02468][048]|[13579][26])$";

// Deal with months with 31 days
var d1 = @"(3[01]|[012]\d|\d)\.(0?[13578]|10|12)\.\d{4}";
// Deak with months with 30 days
var d2 = @"(30|[012]\d|\d)\.(0?[469]|11)\.\d{4}";
// This portion deals with February 29 in leap years
var d3 = @"29\.(0?2)\.\d{2}([02468][048]|[13579][26])";
// Deal with other days in February
var d4 = @"(2[0-8]|[01]\d|\d)\.(0?2)\.\d{4}";
// Full pattern
var date_pattern = $"^({d1}|{d2}|{d3}|{d4})$";

var dates = new[]
{
    "11.12.2001",
    "15.99.2021",
    "14.01.2010",
    "29.02.2020", //leap year
    "29.02.2019", //not a leap year
    "28.02.2019"
};

foreach (var date in dates)
{
    WriteLine($"Date: {date}, Is match: {Regex.IsMatch(date, date_pattern)}");
}

// Output:
// Date: 11.12.2001, Is match: True
// Date: 15.99.2021, Is match: False
// Date: 14.01.2010, Is match: True
// Date: 29.02.2020, Is match: True
// Date: 29.02.2019, Is match: False
// Date: 28.02.2019, Is match: True