获取给定周年，给定月份和给定周的开始和结束日期

如何在c＃4.0中获取给定年份（int），给定月份（int）和给定周（int）{示例年份：2011月份：07周：04}的开始和结束日期？ 提前致谢。

2011年07月的开始日期和月份的周数是04。

Answer 1

谷歌是你的朋友。

月：

public DateTime FirstDayOfMonthFromDateTime(DateTime dateTime) { return new DateTime(dateTime.Year, dateTime.Month, 1); } public DateTime LastDayOfMonthFromDateTime(DateTime dateTime) { DateTime firstDayOfTheMonth = new DateTime(dateTime.Year, dateTime.Month, 1); return firstDayOfTheMonth.AddMonths(1).AddDays(-1); } 

您可以多年来做类似的事情：

  DateTime time = new DateTime(2011,1,1); time.AddYears(1).AddDays(-1); 

一周需要使用CultureInfo.FirstDay（或者你想要设置为一周的第一天，在某些国家是星期一，有时是星期天）。

 /// 
 /// Returns the first day of the week that the specified /// date is in using the current culture. /// 
 public static DateTime GetFirstDayOfWeek(DateTime dayInWeek) { CultureInfo defaultCultureInfo = CultureInfo.CurrentCulture; return GetFirstDateOfWeek(dayInWeek, defaultCultureInfo); } /// 
 /// Returns the first day of the week that the specified date /// is in. /// 
 public static DateTime GetFirstDayOfWeek(DateTime dayInWeek, CultureInfo cultureInfo) { DayOfWeek firstDay = cultureInfo.DateTimeFormat.FirstDayOfWeek; DateTime firstDayInWeek = dayInWeek.Date; while (firstDayInWeek.DayOfWeek != firstDay) firstDayInWeek = firstDayInWeek.AddDays(-1); return firstDayInWeek; } 

Answer 2

不确定，但这是你要追求的吗？

 var weekStart = new DateTime(year, month, 1).AddDays(week * 7); var weekEnd = weekStart.AddDays(6); 

Answer 3

假设你从第1周开始：

 var startDate = new DateTime(year, month, 1).AddDays((week - 1) * 7); var endDate = startDate.AddDays(6); 

Answer 4

你也可以使用

 DateTime.DaysInMonth(int year,int month); 

弄明白。 几周将更加困难。

Answer 5

DateTime计算因为这些有点棘手，我可以想出一些假设

 //assign it to the first day of the month DateTime getweek = new DateTime(2011, 4, 1); // say the week starts on a Sunday while (getweek.DayOfWeek != DayOfWeek.Sunday) getweek = getweek.AddDays(1); DateTimeFormatInfo info = DateTimeFormatInfo.CurrentInfo; Calendar cal = info.Calendar; //Now you are on the first week add 3 more to move to the Fourth week DateTime start = cal.AddWeeks(getweek, 3); // 24 April 2011 DateTime end = start.AddDays(6); // 30 April 2011