using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^
(?=(?:(?![mM]{2}).)*[mM]{2}(?:(?![mM]{2}).)*$)
(?=(?:(?![dD]{2}).)*[dD]{2}(?:(?![dD]{2}).)*$)
(?=(?:(?![yY]{2}(?:[yY]{2})?).)*[yY]{2}(?:[yY]{2})?(?:(?![yY]{2}(?:[yY]{2})?).)*$)
(?:
(?:[mM]{2}|[dD]{2}|[yY]{2}(?:[yY]{2})?)
(?:[_-](?!$))?
){3}
$";
string input = @"The expected result is that only combinations such as the following can test true:
dd-mm-yy
MM-DD_YYYY
yyyy_dd-MM
mmddyy
YYYYddMM
And not something like:
ddyyyyymmmmmmmmm
mmddyymm
ADDITIONAL no-checks:
mmmmmm
yyyymmmm
yydddd
YYYYddMM-
ddyyyy
yyyymm
yyyydd
";
RegexOptions options = RegexOptions.Multiline | RegexOptions.IgnorePatternWhitespace;
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