System.DateTimeUtils.GetStandardPattern C# (CSharp) Method

		public static string GetStandardPattern (char format, DateTimeFormatInfo dfi, out bool useutc, out bool use_invariant, bool date_time_offset)
		{
			String pattern;

			useutc = false;
			use_invariant = false;

			switch (format)
			{
			case 'd':
				pattern = dfi.ShortDatePattern;
				break;
			case 'D':
				pattern = dfi.LongDatePattern;
				break;
			case 'f':
				pattern = dfi.LongDatePattern + " " + dfi.ShortTimePattern;
				break;
			case 'F':
				pattern = dfi.FullDateTimePattern;
				break;
			case 'g':
				pattern = dfi.ShortDatePattern + " " + dfi.ShortTimePattern;
				break;
			case 'G':
				pattern = dfi.ShortDatePattern + " " + dfi.LongTimePattern;
				break;
			case 'm':
			case 'M':
				pattern = dfi.MonthDayPattern;
				break;
#if NET_2_0
			case 'o':
			case 'O':
				pattern = dfi.RoundtripPattern;
				use_invariant = true;
				break;
#endif
			case 'r':
			case 'R':
				pattern = dfi.RFC1123Pattern;
				if (date_time_offset)
					useutc = true;
				use_invariant = true;
				break;
			case 's':
				pattern = dfi.SortableDateTimePattern;
				use_invariant = true;
				break;
			case 't':
				pattern = dfi.ShortTimePattern;
				break;
			case 'T':
				pattern = dfi.LongTimePattern;
				break;
			case 'u':
				pattern = dfi.UniversalSortableDateTimePattern;
				if (date_time_offset)
					useutc = true;
				use_invariant = true;
				break;
			case 'U':
				if (date_time_offset)
					pattern = null;
				else {
//					pattern = dfi.LongDatePattern + " " + dfi.LongTimePattern;
					pattern = dfi.FullDateTimePattern;
					useutc = true;
				}
				break;
			case 'y':
			case 'Y':
				pattern = dfi.YearMonthPattern;
				break;
			default:
				pattern = null;
				break;
//				throw new FormatException (String.Format ("Invalid format pattern: '{0}'", format));
			}

			return pattern;
		}

        public string ToString(string format, IFormatProvider formatProvider)
        {
            DateTimeFormatInfo dfi = DateTimeFormatInfo.GetInstance(formatProvider);

            if (format == null || format == String.Empty)
            {
                format = dfi.ShortDatePattern + " " + dfi.LongTimePattern + " zzz";
            }

            bool to_utc = false, use_invariant = false;

            if (format.Length == 1)
            {
                char fchar = format [0];
                try {
                    format = DateTimeUtils.GetStandardPattern(fchar, dfi, out to_utc, out use_invariant, true);
                } catch {
                    format = null;
                }

                if (format == null)
                {
                    throw new FormatException("format is not one of the format specifier characters defined for DateTimeFormatInfo");
                }
            }
            return(to_utc ? DateTimeUtils.ToString(UtcDateTime, TimeSpan.Zero, format, dfi) : DateTimeUtils.ToString(DateTime, Offset, format, dfi));
        }