Replacing substrings using Regex in C# .NET: date format example

Say your application receives the dates in the following format:

mm/dd/yy

…but what you actually need is this:

dd-mm-yy

You can try and achieve that with string operations such as IndexOf and Replace. You can however perform more sophisticated substring operations using regular expressions. The following method will perform the required change:

private static string ReformatDate(String dateInput)
{
	return Regex.Replace(dateInput, "\\b(?<month>\\d{1,2})/(?<day>\\d{1,2})/(?<year>\\d{2,4})\\b"
		, "${day}-${month}-${year}");
}

Calling this method with “10/28/14” returns “28-10-14”.

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