问在.net中，知道周的数字，我怎样才能得到工作日的日期？

EN

DateTime jan1 = new DateTime(yyyy, 1, 1);

int daysOffset = DayOfWeek.Tuesday - jan1.DayOfWeek;

DateTime firstMonday = jan1.AddDays(daysOffset);

var cal = CultureInfo.CurrentCulture.Calendar;

int firstWeek = cal.GetWeekOfYear(jan1, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

var weekNum = ww;

if (firstWeek <= 1)
{
    weekNum -= 1;
}

var result = firstMonday.AddDays(weekNum * 7 + d - 1);

return result;

var c = CultureInfo.CurrentCulture.Calendar;

// `FromDayOfWeek` fixes problem with the enumeration
// not based on Monday being the first day of the week
d = (byte)FromDayOfWeek(c.GetDayOfWeek(t));
switch (d)
{
    case 1:
    case 2:
    case 3:
        // see this for details
        // http://blogs.msdn.com/shawnste/archive/2006/01/24/iso-8601-week-of-year-format-in-microsoft-net.aspx
        t = t.AddDays(3);
        break;
}

ww = (byte)c.GetWeekOfYear(t, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);

// Adjust year when week 53 occurs in January or week 1 occurs in December 
if (ww == 53 && t.Month == 1)
{
    yyyy = (short)(t.Year - 1);
}
else if (ww == 1 && t.Month == 12)
{
    yyyy = (short)(t.Year + 1);
}
else
{
    yyyy = (short)t.Year;
}