指定周转对应日期

SQL 根据某年某周获取对应日期

--创建一个标量值函数

--例：WeekToDay(2018,18) 

CREATE function [dbo].[WeekToDay](@Year int,@Week int) 
returns varchar(50)
as
begin

declare @Year1 datetime
declare @StratWeek datetime
declare @EndWeek datetime

set @Year1=convert(smalldatetime,convert(varchar(4),@Year) + '-1-1')
set @StratWeek=dateadd(day,1-datePart(weekday,@Year1),dateAdd(week,@Week-1,@Year1))
set @EndWeek=dateadd(day,6,@StratWeek)

RETURN convert(varchar(10),@StratWeek,111)

end

C#  根据某年某周获取对应日期

例：  GetFirstDayOfWeek(year, week, System.Globalization.CultureInfo.InvariantCulture); 

/// <summary>
/// 根据一年中的第几周获取该周的开始日期
/// </summary>
/// <param name="year"></param>
/// <param name="week"></param>
/// <param name="culture"></param>
/// <returns></returns>
public static DateTime GetFirstDayOfWeek(int year, int week, System.Globalization.CultureInfo culture)
{
System.Globalization.Calendar calendar = culture.Calendar;
DateTime firstOfYear = new DateTime(year, 1, 1, calendar);
DateTime targetDay = calendar.AddWeeks(firstOfYear, week - 1);
DayOfWeek firstDayOfWeek = culture.DateTimeFormat.FirstDayOfWeek;

while (targetDay.DayOfWeek != firstDayOfWeek)
{
targetDay = targetDay.AddDays(-1);
}

return targetDay;
}