[C#][Calendar] Comment convertir correctement une date en un numéro de semaine ?

Bonjour,

Je veux convertir une date en numéro de semaine, mon code est les suivant :
Code:

1 2 3 4 5 6 7 8 CultureInfo myCI = CultureInfo.CurrentCulture ; System.Globalization.Calendar myCal = myCI.Calendar; CalendarWeekRule CWR = myCI.DateTimeFormat.CalendarWeekRule; DayOfWeek FirstDOW = myCI.DateTimeFormat.FirstDayOfWeek; int numSemaine = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear (dateRef, CWR, FirstDOW );
Le numéro de semaine est trop grand de 1.
Exp : Pour la date 02/05/2006, il me retourne 19 et pas 18.

Quelles sont les valeurs que tu obtiens pour CWR et FirstDOW ?

Après avoir testé ce code, je constate la même erreur qui est due au fait que CWR est égale à FirstDay alors qu'en France on utilise FirstFourDayWeek.
Le CurrentCulture retourne donc la mauvaise valeur...

C'est un problème du Framework je crois. Je me rappelle avoir lu un article là dessus l'année dernière, c'était avec le Framework 1 il me semble. La méthode GetWeekOfYear() ne renverra jamais un numéro correct (càd ISO 8601, enfin je crois), quelle que soit la culture. A priori le problème est toujours présent sous le Framework 2.

Si je retrouve le lien de l'article je le posterais, mais j'avais toujours le code dans un coin, c'est le plus important ;)

Edit : j'ai retrouvé l'article ici.

Code:

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private static int WeekNumber_Entire4DayWeekRule(DateTime date)
{
    // Updated 2004.09.27. Cleaned the code and fixed a bug.
    // Compared the algorithm with code published here .
    // Tested code successfully against the other algorithm 
    // for all dates in all years between 1900 and 2100.
    // Thanks to Marcus Dahlberg for pointing out the deficient logic.
 
    // Calculates the ISO 8601 Week Number
    // In this scenario the first day of the week is monday, 
    // and the week rule states that:
    // [...] the first calendar week of a year is the one 
    // that includes the first Thursday of that year and 
    // [...] the last calendar week of a calendar year is 
    // the week immediately preceding the first 
    // calendar week of the next year.
    // The first week of the year may thus start in the 
    // preceding year
 
    const int JAN = 1;
    const int DEC = 12;
    const int LASTDAYOFDEC = 31;
    const int FIRSTDAYOFJAN = 1;
    const int THURSDAY = 4;
    bool ThursdayFlag = false;
 
    // Get the day number since the beginning of the year
    int DayOfYear = date.DayOfYear;
 
    // Get the numeric weekday of the first day of the 
    // year (using sunday as FirstDay)
    int StartWeekDayOfYear =
         (int)(new DateTime(date.Year, JAN, FIRSTDAYOFJAN)).DayOfWeek;
    int EndWeekDayOfYear =
         (int)(new DateTime(date.Year, DEC, LASTDAYOFDEC)).DayOfWeek;
 
    // Compensate for the fact that we are using monday
    // as the first day of the week
    if (StartWeekDayOfYear == 0)
        StartWeekDayOfYear = 7;
    if (EndWeekDayOfYear == 0)
        EndWeekDayOfYear = 7;
 
    // Calculate the number of days in the first and last week
    int DaysInFirstWeek = 8 - (StartWeekDayOfYear);
    int DaysInLastWeek = 8 - (EndWeekDayOfYear);
 
    // If the year either starts or ends on a thursday
    // it will have a 53rd week
    if (StartWeekDayOfYear == THURSDAY || EndWeekDayOfYear ==
 THURSDAY)
        ThursdayFlag = true;
 
    // We begin by calculating the number of FULL weeks
    // between the start of the year and our date.
    // The number is rounded up, so the smallest possible value is 0.
    int FullWeeks = (int)Math.Ceiling((DayOfYear - (DaysInFirstWeek)) /
 7.0);
 
    int WeekNumber = FullWeeks;
 
    // If the first week of the year has at least four days, then 
    // the actual week number for our date can be incremented by one.
    if (DaysInFirstWeek >= THURSDAY)
        WeekNumber = WeekNumber + 1;
 
    // If week number is larger than week 52
    // (and the year doesn't either start or end on a thursday)
    // then the correct week number is 1.
    if (WeekNumber > 52 && !ThursdayFlag)
        WeekNumber = 1;
 
    // If week number is still 0, it means that we are trying
    // to evaluate the week number for a week that belongs
    // in the previous year(since that week has 3 days or
    // less in our date's year).
    // We therefore make a recursive call using
    // the last day of the previous year.
    if (WeekNumber == 0)
        WeekNumber = WeekNumber_Entire4DayWeekRule(
             new DateTime(date.Year - 1, DEC, LASTDAYOFDEC));
    return WeekNumber;
}

Code:

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CultureInfo ci = new CultureInfo( "fr-FR" );
int semaine = ci.Calendar.GetWeekOfYear( Calendar1.SelectedDates[0],
 CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday );

Ce code a l'air de mieux marcher...