///
             /// 获得本月有几周
             ///
             ///
             ///
             public  void NumWeeks(DateTime dt)
             {
                 //年
                 int year = dt.Year;
                 //月
                 int month = dt.Month;
                 //当前月第一天
                 DateTime weekStart = new DateTime(year, month, 1);
                 //该月的最后一天
                 DateTime monEnd = weekStart.AddMonths(1).AddDays(-1);
                 int i = 1;
                 //当前月第一天是星期几
                 int dayOfWeek = Convert.ToInt32(weekStart.DayOfWeek.ToString("d"));
                 //该月第一周结束日期
                 DateTime weekEnd = dayOfWeek == 0 ? weekStart : weekStart.AddDays(7 - dayOfWeek);

                 richTextBox2.Text += "第" + i + "周起始日期： " + weekStart.ToShortDateString() + "   结束日期： " + weekEnd.ToShortDateString() + "n";

                 //当日期小于或等于该月的最后一天
                 while (weekEnd.AddDays(1) monEnd ? monEnd : weekEnd.AddDays(7);

                     richTextBox2.Text += "第" + i + "周起始日期： " + weekStart.ToShortDateString() + "   结束日期： " + weekEnd.ToShortDateString() + "n";
                 }

                 richTextBox2.Text += year + "年" + month + "月共有" + i + "周n";
             }