using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^
# Validate the basic structure
(?=\d{1,4}\/\d{1,4}\/\d{1,4}$)
# The below subexpression matches a leap year
# This will be useful later when checking Feb 29th
(?<leap>0*$|\d*(?:[13579][26]|(?:\b|[02468])[048])(?:00|(?<!00))$){0}
# Match and capture a month, saving a 30-day month or Feb for later reference
0*(?<month>(?<thirty>9|4|6|11)|(?<feb>2)|1[02]|[13578])\/
# If Feb was matched and 29 appears, check for a leap year
0*(?<day>[1-9]|1\d|2[0-8]|(?(feb)29(?=\/(?&leap))|(?:29|(?(thirty)30|3[01]))))\/
# Match and capture a year
(?:0\B)*(?<year>\d+)
$";
string input = @"1/25/2018
3/11/2119
6/8/224
6/54/1996
2/29/2004
2/29/1900";
RegexOptions options = RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx