使用.NET计算一个月中的第几周

Question

.NET库是否可以简单地返回给定日期的星期数？例如，输入Year = 2010, Month = 1, Day = 25，应输出5为周数。

最近我发现是Calendar.GetWeekOfYear，这几乎就在那里。

Java有一个日期字符串格式“W”，它在一个月内返回一周，但我在.NET中看不到任何等同的东西。

Answer 1

没有内置的方式来做到这一点，但这里是一个扩展方法，它应该为你做的工作：

static class DateTimeExtensions { 
    static GregorianCalendar _gc = new GregorianCalendar(); 
    public static int GetWeekOfMonth(this DateTime time) { 
     DateTime first = new DateTime(time.Year, time.Month, 1); 
     return time.GetWeekOfYear() - first.GetWeekOfYear() + 1; 
    } 

    static int GetWeekOfYear(this DateTime time) { 
     return _gc.GetWeekOfYear(time, CalendarWeekRule.FirstDay, DayOfWeek.Sunday); 
    } 
} 

用法：

DateTime time = new DateTime(2010, 1, 25); 
Console.WriteLine(time.GetWeekOfMonth()); 

输出：

5 

您可以根据自己的需要更改GetWeekOfYear。

Answer 2

，那么具体：http://forums.asp.net/t/1268112.aspx

你可以使用：

public static int Iso8601WeekNumber(DateTime dt) 
{ 
    return CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(dt, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday); 
} 

public static int GetWeekOfMonth(DateTime dt) 
{  

    int weekOfYear = Iso8601WeekNumber(dt); 

    if (dt.Month == 1) 
    { 
     //week of year == week of month in January 
     //this also fixes the overflowing last December week 
     return weekOfYear; 
    } 

    int weekOfYearAtFirst = Iso8601WeekNumber(dt.AddDays(1 - dt.Day)); 
    return weekOfYear - weekOfYearAtFirst + 1; 
} 

注意认为，由于有一定的算法选择，您的需求可能会有所不同。即是一周的星期一到星期五是二月底还是三月的第一周，或者什么标准定义了一个月的“第一个”星期？ ISO 8601：2004未给出“每周”的定义。

Answer 3

没有直接的内置方式来做到这一点，但它可以很容易地完成。这是一个扩展方法，它可以用来轻松获得日期的年份为基础的周数：

public static int GetWeekNumber(this DateTime date) 
{ 
    return GetWeekNumber(date, CultureInfo.CurrentCulture); 
} 

public static int GetWeekNumber(this DateTime date, CultureInfo culture) 
{ 
    return culture.Calendar.GetWeekOfYear(date, 
     culture.DateTimeFormat.CalendarWeekRule, 
     culture.DateTimeFormat.FirstDayOfWeek); 
} 

然后，我们可以用它来计算月为周数，有点像Jason shows。一个文化友好的版本可能看起来像这样：

public static int GetWeekNumberOfMonth(this DateTime date) 
{ 
    return GetWeekNumberOfMonth(date, CultureInfo.CurrentCulture); 
} 

public static int GetWeekNumberOfMonth(this DateTime date, CultureInfo culture) 
{ 
    return date.GetWeekNumber(culture) 
     - new DateTime(date.Year, date.Month, 1).GetWeekNumber(culture) 
     + 1; // Or skip +1 if you want the first week to be 0. 
} 

Answer 4

这是一个古老的线程，但我需要这样的事情，这就是我想出的。

public static int WeekOfMonth(this DateTime date) 
{ 
    DateTime firstDayOfMonth = new DateTime(date.Year, date.Month, 1); 
    int firstDay = (int)firstDayOfMonth.DayOfWeek; 
    if (firstDay == 0) 
    { 
     firstDay = 7; 
    } 
    double d = (firstDay + date.Day - 1)/7.0; 
    return (int)Math.Ceiling(d); 
} 

注意：如果您想使用星期一作为一周的第一天，这应该有效。如果你想让这个星期在星期天开始，那么在2015年3月的第二个星期以及其他日期可能会失败。 2015年3月9日星期一是第二周的第一天。上述计算在该日期返回“3”。

Answer 5

public int WeekCalc(DateTime dt) 
{ 
    CultureInfo ciCurr = CultureInfo.CurrentCulture; 
    int weekNum = ciCurr.Calendar.GetWeekOfYear(dt, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday); 
    return weekNum; 
} 

Answer 6

@Svish

VB版：

Public Shared Function GetWeekNumber(ByVal [date] As DateTime) As Integer 
    Return GetWeekNumber([date], CultureInfo.CurrentCulture) 
End Function 

Public Shared Function GetWeekNumber(ByVal [date] As DateTime, ByVal culture As CultureInfo) As Integer 
    Return culture.Calendar.GetWeekOfYear([date], culture.DateTimeFormat.CalendarWeekRule, culture.DateTimeFormat.FirstDayOfWeek) 
End Function 

Public Shared Function GetWeekNumberOfMonth(ByVal [date] As DateTime) As Integer 
    Return GetWeekNumberOfMonth([date], CultureInfo.CurrentCulture) 
End Function 

Public Shared Function GetWeekNumberOfMonth(ByVal [date] As DateTime, ByVal culture As CultureInfo) As Integer 
    Return GetWeekNumber([date], culture) - GetWeekNumber(New DateTime([date].Year, [date].Month, 1), culture) + 1 
    ' Or skip +1 if you want the first week to be 0. 
End Function 

Answer 7

一旦你有一个月的第一天的星期几，你可以使用整数运算得到一个月的一周。

static class DateTimeExtensions 
{ 
    // Assumes that in current culture week starts on Sunday 
    public static int GetWeekOfMonth(this DateTimeOffset time) 
    { 
     DateTimeOffset first = new DateTimeOffset(time.Year, time.Month, 1, 0, 0, 0, time.Offset); 
     int firstSunday = (7 - (int)first.DayOfWeek) % 7 + 1; 
     int weekOfMonth = 1 + (time.Day + 7 - firstSunday)/7; 

     return weekOfMonth; 
    } 
} 

Answer 8

一些简单的...:)

private int WeeksNumber() 
     { 
      int daysInMonth = DateTime.DaysInMonth(YourYear, YourMonth); 
      DateTime date = new DateTime(Year, Month, 1); 
      switch (daysInMonth) 
      { 
       case 28: 
        { 
         if (date.DayOfWeek == DayOfWeek.Monday) 
         { 
          return 4; 
         } 
         else 
         { 
          return 5; 
         } 
        } 
       case 29: 
        { 
         return 5; 
        } 
       case 30: 
        { 
         if (date.DayOfWeek == DayOfWeek.Sunday) 
         { 
          return 6; 
         } 
         else 
         { 
          return 5; 
         } 
        } 
       case 31: 
        { 
         if (date.DayOfWeek == DayOfWeek.Sunday || date.DayOfWeek == DayOfWeek.Saturday) 
         { 
          return 6; 
         } 
         else 
         { 
          return 5; 
         } 
        } 
       default: return 5; 
      } 
     } 

Answer 9

标题是误导。问题实际上是关于月份的日历周编号（如果您计算日历中的行的周数），而不是实际的周数。

月内的周数，你可以使用：

VB: 
    Function WeekNumber(TargetDate As Date) As Integer 
     Return (TargetDate.Day - 1) \ 7 + 1 
    End Function 

C#: 
    public int WeekNumber(DateTime TargetDate) 
    { 
     return (TargetDate.Day - 1)/7 + 1; 
    } 

Answer 10

这是我的解决方案：

static string GetWeekNumber() 
    { 

     var weekNumber = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(DateTime.Now, CalendarWeekRule.FirstFourDayWeek, 
      DayOfWeek.Sunday) - 
     CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(DateTime.Now.AddDays(1 - DateTime.Now.Day), 
      CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday) + 1; 

     switch (weekNumber) 
     { 
      case 1 : 
       return "First"; 
      case 2: 
       return "Second"; 
      case 3: 
       return "Third"; 
      default: 
       return "Fourth"; 
     } 
    } 

Answer 11

这里有一个简单的选择，如果你想第7天被认为是第一周，即使一个月不上周日开始：

class Program 
{ 
    static void Main(string[] args) 
    { 
     var dates = Enumerable.Range(0, 10) 
      .Select(r => new DateTime(2015, 10, 1).AddDays(r)) 
      .Select(q => new { Date = q, WeekOfMonth = q.WeekOfMonth() }); 

     foreach(var item in dates) 
     { 
      Console.WriteLine("Date: {0:ddd MM-dd-yyyy}, WOM: {1}", item.Date, item.WeekOfMonth); 
     } 

     var final = Console.ReadLine(); 
    } 
} 

public static class DateTimeExtensions 
{ 
    public static int WeekOfMonth(this DateTime d) 
    { 
     var isExact = (d.Day % 7 == 0); 
     var offset = isExact ? 0 : 1; 
     return (int)Math.Floor(d.Day/7.0) + offset; 
    } 
} 

Answer 12

Dim mdt As Date = txtDT.Text 
    Dim weekNum As Integer = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(mdt, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday) - CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(GetFirstDayOfMonth(mdt), CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday) + 1 
    Response.Write(weekNum)