如何判断一个时间为当年的第几周?

Question

比如： 时间：2010-08-19  为当年的第几周？

Answer 1

dt = DateTime.Today.DayOfWeek.ToString();

Answer 2

            DateTime dt = DateTime.Now;            Console.WriteLine(dt.DayOfYear/7);

Answer 3

http://blog.csdn.net/rubbish_only/archive/2006/09/21/1204520.aspx
参考

Answer 4

  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);
        }
    DateTime dt = Convert.ToDateTime("2010-08-19");
            
            Response.Write(DatePart(dt).ToString());  //结果：34

Answer 5

dayofyear / 7 + (dayofyear % 7) > 0 ? 1 : 0;

Answer 6

public int Weekofyear(DateTime dtime)       
 {      
 int weeknum = 1;   //默认的周数从1开始        
 DateTime firstdate = DateTime.Parse(dtime.Year.ToString() + "-1" + "-1");    
 DayOfWeek firstweek = firstdate .DayOfWeek;   
 for (int i = (int)firstweek + 1; i <= dtime.DayOfYear; i = i + 7)           
 {     
     weeknum = weeknum + 1;           
 }           
 return weeknum ;
}
时间范围

Answer 7

            //目标日期
            DateTime dt = DateTime.Now;            //该年1月1日所在的周，定义为第一周，sunday为0，monday为1
            DateTime dtFirst = new DateTime(dt.Year, 1, 1);            //目标日期距离第一天的天数
            int daysCount = Convert.ToInt32((dt - dtFirst).TotalDays);            //将第一天的日期补齐
            daysCount += Convert.ToInt32(dtFirst.DayOfWeek);            //目标日期所在的周
            int weeksCount = daysCount / 7;            //目标日期所在的天
            int dayIdx = Convert.ToInt32(dt.DayOfWeek);            //显示结果
            Console.WriteLine("日期" + dt.ToShortDateString() + "是第" + (weeksCount + 1).ToString() + "周的第" + dayIdx.ToString() + "天。");