Regex.Replace and String.Replace does not work

Question

I have a string 01-Jan-2014 00:00:00 and I intend to shorten the year into 2 characters.

my code:

DateTime dtParsedDate = new DateTime();
string strInput = "01-Jan-2014 00:00:00";
Regex regDate = new Regex(@"\d{2}-\w{3}-\d{4}");

// parse into datetime object
dtParsedDate = DateTime.ParseExact(regDate.Match(strInput).Value, "dd-MMM-yyyy", CultureInfo.InvariantCulture);

// replace the string with new format
regDate.Replace(arrData[iCol], dtParsedDate.ToString("dd-MMM-yy"));

I've verified that the string is matched correctly using regex.

"01-Jan-2014" did not get replaced into "01-Jan-14". What is wrong with my code?

Read the docs. Regex.Replace returns a new string, it does not mutate the string you pass in to it (because strings are immutable). — Matt Burland
– Matt Burland, Commented Apr 29, 2014 at 13:31

pmcoltrane · Accepted Answer · 2014-04-29 13:31:06Z

2

Regex.Replace and String.Replace do not modify the existing string: they return the modified string. Try changing your code to:

arrData[iCol] = regDate.Replace(arrData[iCol], dtParsedDate.ToString("dd-MMM-yy"));

answered Apr 29, 2014 at 13:31

pmcoltrane

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nvoigt · Accepted Answer · 2014-04-29 13:30:54Z

2

In .NET strings are immutable and all replace methods do not replace in-place but return a new string with the replacements done.

answered Apr 29, 2014 at 13:30

nvoigt

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