Parsing a DateTime containing milliseconds fails for certain cultures. Why?

Question

I'm trying to parse a string containing milliseconds like this:

string s = "11.05.2010 15:03:08.7718687"; // culture: de-CH
DateTime d = DateTime.Parse(s); // works

However, for example under the de-DE locale, the decimal separator is a comma (not a dot). So the example becomes:

string s = "11.05.2010 15:03:08,7718687"; // culture: de-DE (note the comma)
DateTime d = DateTime.Parse(s); // throws a FormatException

It is weird to me that DateTime.Parse(s) should throw a FormatException now as it is supposed to use the CultureInfo.CurrentCulture to do the parsing. Even passing the CurrentCulture as an argument explicitly does not help neither. Does anybody have an idea why this does not work? Doesn't parsing take the NumberFormatInfo.NumberDecimalSeparator into account?

Answer 1

DateTimeFormatInfo applies to formatting/parsing dates, not NumberFormatInfo. DateTimeFormatInfo does not define a "seconds/milliseconds" separator that can be overloaded by different cultures.

None of the Standard Date and Time format strings display the milliseconds, except for roundtrip, which doesn't appear to be culture sensitive anyway. So you shouldn't happen upon a string in that format, unless your own code is generating it. If you know your code is going to generate dates in that format, you can provide a custom format string that uses the comma as the separator between seconds and milliseconds.