c# 擷取某日期所在周的第一天和最後一天

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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(以星期天為第一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekFirstDaySun(DateTime datetime){    //星期天為第一天    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(以星期一為第一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekFirstDayMon(DateTime datetime){    //星期一為第一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    //因為是以星期一為第一天，所以要判斷weeknow等於0時，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>/// 得到本周最後一天(以星期六為最後一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekLastDaySat(DateTime datetime){    //星期六為最後一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    int daydiff = (7 - weeknow) - 1;    //本周最後一天    string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");    return Convert.ToDateTime(LastDay);}/// <summary>/// 得到本周最後一天(以星期天為最後一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekLastDaySun(DateTime datetime){    //星期天為最後一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    weeknow = (weeknow == 0 ? 7 : weeknow);    int daydiff = (7 - weeknow);    //本周最後一天    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(以星期天為第一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekFirstDaySun(DateTime datetime){    //星期天為第一天    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(以星期一為第一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekFirstDayMon(DateTime datetime){    //星期一為第一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    //因為是以星期一為第一天，所以要判斷weeknow等於0時，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>/// 得到本周最後一天(以星期六為最後一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekLastDaySat(DateTime datetime){    //星期六為最後一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    int daydiff = (7 - weeknow) - 1;    //本周最後一天    string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");    return Convert.ToDateTime(LastDay);}/// <summary>/// 得到本周最後一天(以星期天為最後一天)/// </summary>/// <param name="datetime"></param>/// <returns></returns>public DateTime GetWeekLastDaySun(DateTime datetime){    //星期天為最後一天    int weeknow = Convert.ToInt32(datetime.DayOfWeek);    weeknow = (weeknow == 0 ? 7 : weeknow);    int daydiff = (7 - weeknow);    //本周最後一天    string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");    return Convert.ToDateTime(LastDay);}}}

 

c# 擷取某日期所在周的第一天和最後一天