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;  }