ASP.NET判断当前日期是第几周

/// <summary>
    /// 获取该月中是第几周
    /// </summary>
    /// <param name="day">日期</param>
    /// <returns></returns>
    private int WeekOfMonth(System.DateTime day)
    {
        string y = day.Year.ToString();
        string m = day.Month.ToString();
        string s = y + "-" + m + "-1";

        DateTime dt = DateTime.Parse(s);

        int d = day.Day - dt.Day;
        int w = 1;
        for (int i = 1; i <= d; i++)
        {
            DateTime dt1 = dt.AddDays(i);
            if (dt1.DayOfWeek == DayOfWeek.Sunday)
            {
                w = w + 1;
            }
        }
        return w;
    }

    /// <summary>
    /// 获取该年中是第几周
    /// </summary>
    /// <param name="day">日期</param>
    /// <returns></returns>
    private int WeekOfYear(System.DateTime day)
    {
        int weeknum;
        System.DateTime fDt = DateTime.Parse(day.Year.ToString() + "-01-01");
        int k = Convert.ToInt32(fDt.DayOfWeek);//得到该年的第一天是周几 
        if (k == 0)
        {
            k = 7;
        }
        int l = Convert.ToInt32(day.DayOfYear);//得到当天是该年的第几天 
        l = l - (7 - k + 1);
        if (l <= 0)
        {
            weeknum = 1;
        }
        else
        {
            if (l % 7 == 0)
            {
                weeknum = l / 7 + 1;
            }
            else
            {
                weeknum = l / 7 + 2;//不能整除的时候要加上前面的一周和后面的一周 
            }
        }
        return weeknum; 
    }

第二种方法：double s = System.Math.Floor((double)((Convert.ToDateTime(this.txtStarttime.Text).DayOfYear) + (Convert.ToInt32(Convert.ToDateTime(Convert.ToDateTime(this.txtStarttime.Text).Year.ToString() + "-1-1").DayOfWeek)) - 1) / 7) + 1;