C#如何获取指定周的日期范围

1. 不允许跨年

1) 第一周的第一天从每年的第一天开始，最后一周的最后一天为每年的最后一天。

 static void Main(string[] args)
 {
     DateTime first, last;
     , , ,  };
     , ,  };
     foreach (int y in years)
     {
         foreach (int w in weeks)
         {
             bool result = CalcWeekDay(y, w, out first, out last);
             Console.WriteLine("{0}第{1}周（{2:yyyy-MM-dd} ~ {3:yyyy-MM-dd}） --{4}", y, w, first, last, result);
         }
         Console.WriteLine();
     }
 }

 public static bool CalcWeekDay(int year, int week, out DateTime first, out DateTime last)
 {
     first = DateTime.MinValue;
     last = DateTime.MinValue;
     //年份超限
      || year > ) return false;
     //周数错误
      || week > ) return false;
     //指定年范围
     DateTime start = , );
     DateTime end = , );
     int startWeekDay = (int)start.DayOfWeek;

     )
     {
         first = start;
         last = start.AddDays( - startWeekDay);
     }
     else
     {
         //周的起始日期
         first = start.AddDays(( - startWeekDay) + (week - ) * );
         last = first.AddDays();
         if (last > end)
         {
             last = end;
         }
     }
     return (first <= end);  

2) 程序执行结果

2. 允许跨年

1) 每年的尾周剩余天数计入下一年第一周。

 public static bool CalcWeekDay(int year, int week, out DateTime first, out DateTime last)
 {
     first = DateTime.MinValue;
     last = DateTime.MinValue;
     //年份超限
      || year > ) return false;
     //周数错误
      || week > ) return false;
     //指定年范围
     DateTime start = , );
     DateTime end = , );
     int startWeekDay = (int)start.DayOfWeek;
     //周的起始日期
     first = start.AddDays(( - startWeekDay) + (week - ) * );
     last = first.AddDays();
     //结束日期跨年
     return (last <= end);
 }  

2) 程序执行结果