c# datetime是一年中的第几周

public static int WeekOfYear(DateTime dt, CultureInfo ci)
{
return ci.Calendar.GetWeekOfYear(dt, ci.DateTimeFormat.CalendarWeekRule, ci.DateTimeFormat.FirstDayOfWeek);
}

调用：

//weekOfYear 第几周
int weekOfYear = WeekOfYear(dt_begin, new CultureInfo("zh-CN"));