C#--获取时间段：今天，昨天，本周，上周，本月，上月，本季度，上季度，今年，去年

参考：https://www.iteye.com/blog/xqf222-1920357

https://blog.csdn.net/u011981242/article/details/51595546

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/// <summary> /// 获取时间段（某段时间的0时0分0秒-23时59分59秒） /// </summary> public class DateTimeHelper {     /// <summary>     /// 当前时间     /// </summary>   //public  static DateTime dt = DateTime.Now; //当前时间        //DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") //24小时制     //DateTime.Now.ToString("yyyy-MM-dd hh:mm:ss")  //12小时制        /// <summary>     /// 今天开始,0时0分0秒：     /// </summary>     public static DateTime startCurrentDay= Convert.ToDateTime(DateTime.Now.ToString("D").ToString());       /// <summary>     /// 今天结束,23时59分59秒：     /// </summary>     //public static DateTime endCurrentDay = Convert.ToDateTime(DateTime.Now.AddDays(1).ToString("D").ToString()).AddSeconds(-1);     //public static DateTime endCurrentDay = DateTime.Now.Date.AddDays(1).AddSeconds(-1);     public static DateTime endCurrentDay = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, 23, 59, 59);       /// <summary>     /// 昨天开始     /// </summary>     public static DateTime startLastDay = DateTime.Now.AddDays(-1).Date;       /// <summary>     /// 昨天结束     /// </summary>     public static DateTime endLastDay = startLastDay.AddDays(1).AddSeconds(-1);         /// <summary>     /// 今天星期几     /// </summary>     public static int currentDayOfWeek = Convert.ToInt32(DateTime.Now.DayOfWeek.ToString("d"));       /// <summary>     /// 本周周一     /// </summary>     public static DateTime startCurrentWeek = DateTime.Now.AddDays(1 - ((currentDayOfWeek == 0) ? 7 : currentDayOfWeek)).Date;        /// <summary>     /// 本周周日     /// </summary>     public static DateTime endCurrentWeek = startCurrentWeek.AddDays(7).AddSeconds(-1);         /// <summary>     /// 上周周一     /// </summary>     public static DateTime startLastWeek = startCurrentWeek.AddDays(-7).Date;        /// <summary>     /// 上周周日     /// </summary>     public static DateTime endLastWeek = startLastWeek.AddDays(7).AddSeconds(-1);       /// <summary>     /// 本月月初     /// </summary>     public static DateTime startCurrentMonth = DateTime.Now.AddDays(1 - DateTime.Now.Day).Date; //本月月初        /// <summary>     /// 本月月末     /// </summary>     public static DateTime endCurrentMonth = DateTime.Now.AddDays(1 - DateTime.Now.Day).Date.AddMonths(1).AddSeconds(-1); //本月月末  //DateTime endMonth = startMonth.AddDays((dt.AddMonths(1) - dt).Days - 1);  //本月月末          /// <summary>     /// 上月月初     /// </summary>     public static DateTime startLastMonth = DateTime.Now.AddMonths(-1).Date.AddDays(1 - DateTime.Now.Day);       /// <summary>     /// 上月月末     /// </summary>     public static DateTime endLastMonth = DateTime.Parse(DateTime.Now.AddDays(1 - DateTime.Now.Day).ToShortDateString()).AddSeconds(-1);       /// <summary>     /// 本季度初     /// </summary>     public static DateTime startCurrentQuarter = DateTime.Now.AddMonths(0 - (DateTime.Now.Month - 1) % 3).AddDays(1 - DateTime.Now.Day).Date; //本季度初        /// <summary>     /// 本季度末     /// </summary>     public static DateTime endCurrentQuarter = startCurrentQuarter.AddMonths(3).AddSeconds(-1); //本季度末         /// <summary>     /// 上季度初     /// </summary>     public static DateTime startLastQuarter = startCurrentQuarter.AddMonths(-3).Date;       /// <summary>     /// 上季度末     /// </summary>     public static DateTime endLastQuarter = startLastQuarter.AddMonths(3).AddSeconds(-1);         /// <summary>     /// 今年年初     /// </summary>     public static DateTime startCurrentYear = new DateTime(DateTime.Now.Year, 1, 1).Date; //本年年初       /// <summary>     /// 今年年末     /// </summary>     public static DateTime endCurrentYear = new DateTime(DateTime.Now.Year, 12,31, 23, 59, 59); //本年年末       /// <summary>     /// 去年年初     /// </summary>     public static DateTime startLastYear = startCurrentYear.AddYears(-1).Date;       /// <summary>     /// 去年年末     /// </summary>     public static DateTime endLastYear = endCurrentYear.AddYears(-1);       //至于昨天、明天、上周、上月、上季度、上年度等等，只要AddDays()、AddMonths()、AddYears()这几种方法组合一下就可以了。   }