问从数据库中获取排除天数而不是列表

EN

    List<DateTime> Holidays = new List<DateTime>() 
    { 
        new DateTime(2014, 01, 01), 
        new DateTime(2014, 04, 18), 
        new DateTime(2014, 12, 24), 
        new DateTime(2014, 12, 25), 
        new DateTime(2014, 12, 26),
        new DateTime(2014, 12, 31) 
    };

    public Form1()
    {
       InitializeComponent();
    }

    DateTime AddBusinessDays(int days, DateTime starDate)
    {          
        DateTime tempdt = new DateTime(starDate.Year, starDate.Month, starDate.Day);           
        tempdt = ExHolidays(tempdt, Holidays);
        if (tempdt > starDate.Date && !(days == 0))
             tempdt = tempdt.AddDays(-1);
        days = days - 1;
        while (days > 0)
        {
             tempdt = tempdt.AddDays(1);
             // ja sakuma diena ir brivdiena >>> nakamas darbadienas -1
             tempdt = ExHolidays(tempdt, Holidays);
             days = days - 1;
         }          
        return tempdt;            
    }

    DateTime ExHolidays(DateTime startDate, List<DateTime> holidays)
    {
        while (!IsWorkDay(startDate, holidays))
        {
            startDate = startDate.AddDays(1);
        }
        return startDate;
    }

    bool IsWorkDay(DateTime startDate, List<DateTime> holidays)
    {          
        if ((startDate.DayOfWeek == DayOfWeek.Saturday || startDate.DayOfWeek == DayOfWeek.Sunday ||holidays.Contains(startDate)))
        {
            return false;
        }
        else
        {
            return true;
        }
    }

dateTimePicker2.Value = AddBusinessDays(30, dateTimePicker1.Value);