实现

/// <summary>
        /// 把浮点数格式化为{H:min:s.ms}格式的字符串
        /// </summary>
        /// <param name="f">要格式化的浮点数</param>
        /// <returns>返回格式化后的字符串</returns>
        public static string FormatFloatToDateTimeString(double f)
        {
            string result = String.Empty;
            int day = (int)f / 3600 / 24;
            int hour = ((int)f / 3600 % 24);
            int min = ((int)f % 3600) / 60;
            int sec = (int)f % 60;
            int ms = (int)Math.Round((f - (int)f) * 1000, 0, MidpointRounding.AwayFromZero);

            if (day > 0)
            {
                result = String.Format("{0}.{1}:{2}:{3}.{4}", day, DataProcessor.FillZero(hour.ToString(), 2), DataProcessor.FillZero(min.ToString(), 2), DataProcessor.FillZero(sec.ToString(), 2), DataProcessor.FillZero(ms.ToString(), 3));
            }
            else
            {
                result = String.Format("{0}:{1}:{2}.{3}", DataProcessor.FillZero(hour.ToString(), 2), DataProcessor.FillZero(min.ToString(), 2), DataProcessor.FillZero(sec.ToString(), 2), DataProcessor.FillZero(ms.ToString(), 3));
            }
            return result;
        }