asp.net 取当前第几周

 ///   <summary>  
    ///   返回一个数组长度为3的字符串数组  
    ///   </summary>  
    ///   <returns>GetWeekDay[0]=周次;GetWeekDay[1]=该周第一天;GetWeekDay[2]=该周最后一天</returns>  
    public string[] GetWeekDay()
    {
        string[] inti = new string[3];
        DateTime day = DateTime.Parse(DateTime.Today.Year + "-1-1");
        System.DayOfWeek dateTime = day.DayOfWeek;
        int DayCount = DateTime.Today.DayOfYear;
        int i = (DayCount + aa(dateTime) - 2) / 7 + 1;
        inti[0] = i.ToString();

        inti[1] = day.AddDays(DayCount - 1).ToString("yyyy年MM月dd日");
        inti[2] = day.AddDays(DayCount + 5).ToString("yyyy年MM月dd日");
        Response.Write("第"+i+"周"); 
     
        return inti;
    }

    private int aa(System.DayOfWeek weekday)
    {
        switch (weekday.ToString())
        {
            case "Sunday":
                return 1;
            case "Monday":
                return 2;
            case "Tuesday":
                return 3;
            case "Wednesday":
                return 4;
            case "Thursday":
                return 5;
            case "Friday":
                return 6;
            case "Saturday":
                return 0;
            default:
                return 8;
        }

    }