C# 獲取本周一的時間（時分秒為00:00:00）

 /// <summary>
        /// 獲取本周的周一日期
        /// </summary>
        /// <returns></returns>
        public  string GetThisWeekMonday()
        {
            DateTime date = DateTime.Now;
            DateTime firstDate = System.DateTime.Now;
            switch (date.DayOfWeek)
            {
                case System.DayOfWeek.Monday:
                    firstDate = date;
                    break;
                case System.DayOfWeek.Tuesday:
                    firstDate = date.AddDays(-1);
                    break;
                case System.DayOfWeek.Wednesday:
                    firstDate = date.AddDays(-2);
                    break;
                case System.DayOfWeek.Thursday:
                    firstDate = date.AddDays(-3);
                    break;
                case System.DayOfWeek.Friday:
                    firstDate = date.AddDays(-4);
                    break;
                case System.DayOfWeek.Saturday:
                    firstDate = date.AddDays(-5);
                    break;
                case System.DayOfWeek.Sunday:
                    firstDate = date.AddDays(-6);
                    break;
            }
            return firstDate.ToString("D");
        }