c# - Get just the hour of day from DateTime using either 12 or 24 hour format as defined by the current culture

Question

.Net has the built in ToShortTimeString() function for DateTime that uses the CultureInfo.CurrentCulture.DateTimeFormat.ShortTimePattern format. It returns something like this for en-US: "5:00 pm". For a 24 hour culture such as de-DE it would return "17:00".

What I want is a way to just return just the hour (So "5 pm" and "17" in the cases above) that works with every culture. What's the best/cleanest way to do this?

Thanks!

Answer 1

// displays "15" because my current culture is en-GB
Console.WriteLine(DateTime.Now.ToHourString());

// displays "3 pm"
Console.WriteLine(DateTime.Now.ToHourString(new CultureInfo("en-US")));

// displays "15"
Console.WriteLine(DateTime.Now.ToHourString(new CultureInfo("de-DE")));

// ...

public static class DateTimeExtensions
{
    public static string ToHourString(this DateTime dt)
    {
        return dt.ToHourString(null);
    }

    public static string ToHourString(this DateTime dt, IFormatProvider provider)
    {
        DateTimeFormatInfo dtfi = DateTimeFormatInfo.GetInstance(provider);

        string format = Regex.Replace(dtfi.ShortTimePattern, @"[^hHts]", "");
        format = Regex.Replace(format, @"s+", " ").Trim();

        if (format.Length == 0)
            return "";

        if (format.Length == 1)
            format = '%' + format;

        return dt.ToString(format, dtfi);
    }
}