System.DateTimeFormat.Format C# (CSharp) Méthode

        internal static String Format(DateTime dateTime, String format, DateTimeFormatInfo dtfi)
        {            
            if (format==null || format.Length==0) {
                format = "G";            
                if (dateTime.Ticks < Calendar.TicksPerDay) {
                    //
                    switch (dtfi.Calendar.ID) {
                        case Calendar.CAL_JAPAN: 
                        case Calendar.CAL_TAIWAN:
                        case Calendar.CAL_HIJRI:
                        case Calendar.CAL_HEBREW:
                        case Calendar.CAL_JULIAN:
                            format = "s";
                            break;                        
                    }
                }
            }            

            if (format.Length == 1) {
                format = ExpandPredefinedFormat(format, ref dateTime, ref dtfi);
            } 
            
            return (FormatCustomized(dateTime, format, dtfi));
        }
    

 public String ToString(String format, IFormatProvider formatProvider)
 {
     return(DateTimeFormat.Format(ClockDateTime, format, DateTimeFormatInfo.GetInstance(formatProvider), Offset));
 }