c# - Parse exact custom time format?

Question

I can't seem to get the custom format right for my TimeSpan.ParseExact():

Time samples to be expected:

1:23:45.6
23:45.6
23:45
1:23:45

The string format I'm using:

string withTenthFormat = @"[%h:]mm:ss[.%f]";

Trying to have hours and fractions of seconds optionally. However using this format and an CultureInfo.InvariantCulture does lead to a FormatException. What am I missing?

Answer 1

I'm not aware of the ability to specify optional parts like that in a custom format string. I suggest you use multiple format strings, and use the overload of TimeSpan.ParseExact that takes an array of formats.

string[] formats = { @"h:mm:ss.FFF", @"mm:ss.FFF",
                     @"h:mm:ss", @"mm:ss"};
string[] values = { "1:23:45.6", "23:45.6", "23:45", "1:23:45" };

foreach (string value in values)
{
    var parsed = TimeSpan.ParseExact(value, formats,
                                     CultureInfo.InvariantCulture);
    Console.WriteLine(parsed);
}

(I'm using FFF as the milliseconds specifier to allow you to express "1:23:45.67" as well. If you only ever want hundreds of milliseconds, F or f would be fine.)