C#中怎么计算当前日期是在一年中的第几周

方法一：



private int WeekOfYear(string date)
{
DateTime curDay = Convert.ToDateTime(date);

int firstdayofweek = Convert.ToInt32(Convert.ToDateTime(curDay.Year.ToString() + "- " + "1-1 ").DayOfWeek);

int days = curDay.DayOfYear;
int daysOutOneWeek = days - (7 - firstdayofweek);

if (daysOutOneWeek <= 0)
{
return 1;
}
else
{
int weeks = daysOutOneWeek / 7;
if (daysOutOneWeek % 7 != 0)
weeks ++;

return weeks + 1;
}
}

方法二：



System.Globalization.GregorianCalendar gc = new System.Globalization.GregorianCalendar();
int weekOfYear = gc.GetWeekOfYear(DateTime.Now, System.Globalization.CalendarWeekRule.FirstDay, DayOfWeek.Monday);