C#如何获取指定周的日期范围

Posted 2020-08-31

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。

 1 static void Main(string[] args)  
 2 {  
 3     DateTime first, last;  
 4     int[] years = new int[] { 2015, 2016, 2017, 2018 };  
 5     int[] weeks = new int[] { 1, 52, 53 };  
 6     foreach (int y in years)  
 7     {  
 8         foreach (int w in weeks)  
 9         {  
10             bool result = CalcWeekDay(y, w, out first, out last);  
11             Console.WriteLine("{0}第{1}周（{2:yyyy-MM-dd} ~ {3:yyyy-MM-dd}） --{4}", y, w, first, last, result);  
12         }  
13         Console.WriteLine();  
14     }  
15 }  
16    
17 public static bool CalcWeekDay(int year, int week, out DateTime first, out DateTime last)  
18 {  
19     first = DateTime.MinValue;  
20     last = DateTime.MinValue;  
21     //年份超限  
22     if (year < 1700 || year > 9999) return false;  
23     //周数错误  
24     if (week < 1 || week > 53) return false;  
25     //指定年范围  
26     DateTime start = new DateTime(year, 1, 1);  
27     DateTime end = new DateTime(year, 12, 31);  
28     int startWeekDay = (int)start.DayOfWeek;  
29    
30     if (week == 1)  
31     {  
32         first = start;  
33         last = start.AddDays(6 - startWeekDay);  
34     }  
35     else  
36     {  
37         //周的起始日期  
38         first = start.AddDays((7 - startWeekDay) + (week - 2) * 7);  
39         last = first.AddDays(6);  
40         if (last > end)  
41         {  
42             last = end;  
43         }  
44     }  
45     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。

 1 public static bool CalcWeekDay(int year, int week, out DateTime first, out DateTime last)  
 2 {  
 3     first = DateTime.MinValue;  
 4     last = DateTime.MinValue;  
 5     //年份超限  
 6     if (year < 1700 || year > 9999) return false;  
 7     //周数错误  
 8     if (week < 1 || week > 53) return false;  
 9     //指定年范围  
10     DateTime start = new DateTime(year, 1, 1);  
11     DateTime end = new DateTime(year, 12, 31);  
12     int startWeekDay = (int)start.DayOfWeek;  
13     //周的起始日期  
14     first = start.AddDays((7 - startWeekDay) + (week - 2) * 7);  
15     last = first.AddDays(6);  
16     //结束日期跨年  
17     return (last <= end);  
18 }  

 

2) 程序执行结果