Convert 20121004 (yyyyMMdd) to a valid date time?

Question

I have a string in the following format yyyyMMdd and I am trying to get it to look like this:

yyyy-MM-dd

When I try:

Answer 1

Just use the DateTime.ParseExact method:

string date = "20121004";

string result = DateTime.ParseExact(date, "yyyyMMdd",
                CultureInfo.InvariantCulture).ToString("yyyy-MM-dd");

This also provides the advantage of validating the date before reformatting it with the hyphens. ParseExact throws an exception you can catch, if the date is not in valid range, or the format does not match.