格式化日期时间 计算时间差

/// <summary>
        /// 格式化日期时间
        /// </summary>
        /// <param name="dateTime1">日期时间</param>
        /// <param name="dateMode">显示模式</param>
        /// <returns>0-9种模式的日期</returns>
        public static string FormatDate(DateTime dateTime1, string dateMode)
        {
            switch (dateMode)
            {
                case "0":
                    return dateTime1.ToString("yyyy-MM-dd");
                case "1":
                    return dateTime1.ToString("yyyy-MM-dd HH:mm:ss");
                case "2":
                    return dateTime1.ToString("yyyy/MM/dd");
                case "3":
                    return dateTime1.ToString("yyyy年MM月dd日");
                case "4":
                    return dateTime1.ToString("MM-dd");
                case "5":
                    return dateTime1.ToString("MM/dd");
                case "6":
                    return dateTime1.ToString("MM月dd日");
                case "7":
                    return dateTime1.ToString("yyyy-MM");
                case "8":
                    return dateTime1.ToString("yyyy/MM");
                case "9":
                    return dateTime1.ToString("yyyy年MM月");
                default:
                    return dateTime1.ToString();
            }

 /// <summary>
        /// 计算时间差
        /// </summary>
        /// <param name="DateTime1">时间1</param>
        /// <param name="DateTime2">时间2</param>
        /// <returns></returns>
        public static double DateDiff(DateTime DateTime1, DateTime DateTime2)
        {
            double dateDiff = 0;
            try
            {
                TimeSpan ts1 = new TimeSpan(DateTime1.Ticks);
                TimeSpan ts2 = new TimeSpan(DateTime2.Ticks);
                TimeSpan ts = ts1.Subtract(ts2).Duration();
                dateDiff = ts.TotalSeconds;
            }
            catch
            {

            }
            return dateDiff;
        }