c# 获取某日期所在周的第一天和最后一天

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace WyfClass { public class tools { /// <summary> /// 得到本周第一天(以星期天为第一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekFirstDaySun(DateTime datetime) {     //星期天为第一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     int daydiff = (-1) * weeknow;     //本周第一天     string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(FirstDay); } /// <summary> /// 得到本周第一天(以星期一为第一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekFirstDayMon(DateTime datetime) {     //星期一为第一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     //因为是以星期一为第一天，所以要判断weeknow等于0时，要向前推6天。     weeknow = (weeknow == 0 ? (7 - 1) : (weeknow - 1));     int daydiff = (-1) * weeknow;     //本周第一天     string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(FirstDay); } /// <summary> /// 得到本周最后一天(以星期六为最后一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekLastDaySat(DateTime datetime) {     //星期六为最后一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     int daydiff = (7 - weeknow) - 1;     //本周最后一天     string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(LastDay); } /// <summary> /// 得到本周最后一天(以星期天为最后一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekLastDaySun(DateTime datetime) {     //星期天为最后一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     weeknow = (weeknow == 0 ? 7 : weeknow);     int daydiff = (7 - weeknow);     //本周最后一天     string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(LastDay); } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace WyfClass { public class tools { /// <summary> /// 得到本周第一天(以星期天为第一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekFirstDaySun(DateTime datetime) {     //星期天为第一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     int daydiff = (-1) * weeknow;     //本周第一天     string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(FirstDay); } /// <summary> /// 得到本周第一天(以星期一为第一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekFirstDayMon(DateTime datetime) {     //星期一为第一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     //因为是以星期一为第一天，所以要判断weeknow等于0时，要向前推6天。     weeknow = (weeknow == 0 ? (7 - 1) : (weeknow - 1));     int daydiff = (-1) * weeknow;     //本周第一天     string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(FirstDay); } /// <summary> /// 得到本周最后一天(以星期六为最后一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekLastDaySat(DateTime datetime) {     //星期六为最后一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     int daydiff = (7 - weeknow) - 1;     //本周最后一天     string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(LastDay); } /// <summary> /// 得到本周最后一天(以星期天为最后一天) /// </summary> /// <param name="datetime"></param> /// <returns></returns> public DateTime GetWeekLastDaySun(DateTime datetime) {     //星期天为最后一天     int weeknow = Convert.ToInt32(datetime.DayOfWeek);     weeknow = (weeknow == 0 ? 7 : weeknow);     int daydiff = (7 - weeknow);     //本周最后一天     string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");     return Convert.ToDateTime(LastDay); } } }

 

转载于:https://www.cnblogs.com/bennylam/p/4181354.html

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