时间扩展函数！

 

//本周是本年第几周

private int DatePart(System.DateTime dt)   {    int weeknow = Convert.ToInt32(dt.DayOfWeek);//今天星期几    int daydiff = (-1) * (weeknow+1);//今日与上周末的天数差    int days = System.DateTime.Now.AddDays(daydiff).DayOfYear;//上周末是本年第几天    int weeks = days/7;    if(days%7 != 0)    {     weeks++;    }    //此时，weeks为上周是本年的第几周    return (weeks+1);   }

  //本周起止日期

 private string WeekRange(System.DateTime dt)   {    int weeknow = Convert.ToInt32(dt.DayOfWeek);    int daydiff = (-1) * weeknow;    int dayadd = 6-weeknow;    string dateBegin = System.DateTime.Now.AddDays(daydiff).Date.ToString("MM月dd日");    string dateEnd = System.DateTime.Now.AddDays(dayadd).Date.ToString("MM月dd日");    return dateBegin + " - " +dateEnd;   }