c# - 現在の日付を使用して週を検索していますか? C＃で？

Question

C# で現在の日付の週を見つけるにはどうすればよいですか。現在の日付の週番号を取得しようとしています。

Answer 1

Calendar.GetWeekOfYearを参照してください。

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
      DateTime date1 = new DateTime(2011, 1, 1);
      Calendar cal = dfi.Calendar;

      Console.WriteLine("{0:d}: Week {1} ({2})", date1, 
                        cal.GetWeekOfYear(date1, dfi.CalendarWeekRule, 
                                          dfi.FirstDayOfWeek),
                        cal.ToString().Substring(cal.ToString().LastIndexOf(".") + 1));       
   }
}
// The example displays the following output:
//       1/1/2011: Week 1 (GregorianCalendar)

Answer 2

現在の週の「グローバル」番号が必要な場合は、これを使用できます。

using System;
using System.Globalization;    

DateTime date = DateTime.Now;
int res = 0;

// First day of year
res = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date, CalendarWeekRule.FirstDay, DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek);

// (Default) First four day week from Sunday
res = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday);

// First four day week from StartOfWeek
res = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date, CalendarWeekRule.FirstFourDayWeek, DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek);

// First full week from Sunday
res = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date, CalendarWeekRule.FirstFullWeek, DayOfWeek.Sunday);

// First full week from StartOfWeek
res = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(date, CalendarWeekRule.FirstFullWeek, DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek); 

月の週番号が必要な場合は、次のようなコードを使用します。

 DateTime beginningOfMonth = DateTime.Now;

 while (date.Date.AddDays(1).DayOfWeek != CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
     date = date.AddDays(1);

 int result = (int)Math.Truncate((double)date.Subtract(beginningOfMonth).TotalDays / 7f) + 1;