Question

我只希望获得整年的几周，我想在C＃中获得开始日期（星期一）和结束日期（星期五）。例如：1/52 = 02 Jan (Monday) - 09 Jan (Sunday) 2/52 = 10 Jan (Monday) - 17 Jan (Sunday) 等等。我可以获取当前的星期日期，但不知道该如何获取年份。

// We Set the Monday as the first day of the week.
DayOfWeek day = datetime.DayOfWeek;
int days = day - DayOfWeek.Monday;
if (days == -1)
{
    days = 6;  // this is when we have sunday as a DayOfWeek day
}

DateTime start = datetime.AddDays(-days);
DateTime end = start.AddDays(6);

Answer 1

无需复杂，您可以像下面这样简单地使用while。

while (datetime.DayOfWeek != DayOfWeek.Monday)
{
    datetime= datetime.AddDays(1);
}

DateTime start = datetime;
DateTime end = start.AddDays(6);

或者您想从星期索引1/52中查找任何year的星期，然后编写如下函数。与GetWeek(1, 2020)一样使用它来获取06.01.2020 - 12.01.2020。根据您的要求对其进行格式化。

public DateTime GetNextMonday(DateTime datetime)
{        
    return datetime.AddDays((7 - (int)datetime.DayOfWeek + (int)DayOfWeek.Monday) % 7);
}

public string GetWeek(int week, int year) 
{
    var start = GetNextMonday(new DateTime(year, 1, 1).AddDays((week-1)*7));
    var end = start.AddDays(6);
    return start.ToShortDateString() + " - " + end.ToShortDateString();
}

Answer 2

您可以使用以下方法来计算一年中任何一周的开始日期

public static DateTime StartOfNthWeekOfYear(int year, int weekNumber, DayOfWeek firstDayOfWeek)
{
    if(weekNumber < 1)
    {
        throw new ArgumentOutOfRangeException(nameof(weekNumber));
    }
    DateTime startOfWeek = StartOfFirstWeekOfYear(year, firstDayOfWeek).AddDays((weekNumber - 1) * 7);
    DateTime endOfWeek = startOfWeek.AddDays(6);
    if(endOfWeek.Year != year || startOfWeek.Year != year)
    {
        throw new ArgumentOutOfRangeException(nameof(weekNumber));
    }
    return startOfWeek;
}

public static DateTime StartOfFirstWeekOfYear(int year, DayOfWeek firstDayOfWeek)
{
    DateTime startOfYear = new DateTime(year, 1, 1);
    if (startOfYear.DayOfWeek != firstDayOfWeek)
    {
        return StartOfWeek(startOfYear, firstDayOfWeek).AddDays(7);
    }
    return startOfYear;
}

public static DateTime StartOfWeek(DateTime value, DayOfWeek firstDayOfWeek)
{
    if (value.DayOfWeek != firstDayOfWeek)
    {
        return value.AddDays(-((7 + (int)value.DayOfWeek - (int)firstDayOfWeek) % 7));
    }
    return value;
}

Answer 3

据我所知，这可能会有所帮助，我尝试了以下操作，并为我显示了指定年份的开始和结束日期：

    private System.IO.StreamReader stdinsr = new System.IO.StreamReader(Console.OpenStandardInput());
    [DebuggerHidden]
    private string ReadLine() {
        return stdinsr.ReadLineAsync().Result;
    }

    protected override void OnExit(ExitEventArgs e) {
        base.OnExit(e);

        commandLooper.Abort();
        stdinsr.Dispose();
    }

Answer 4

我认为这应该适用于公历，并考虑到不同的文化：

public static IList<DateTime> GetFirstDayOfWeekDates(CultureInfo cultureInfo, int year)
{
    var lastDateOfYear = new DateTime(year, 12, 31);
    var firstDate = new DateTime(year, 1, 1);
    var dayOfWeek = cultureInfo.DateTimeFormat.FirstDayOfWeek;

    while (firstDate.DayOfWeek != dayOfWeek)
    {
        firstDate = firstDate.AddDays(1);
    }
        
    var numberOfWeeksInYear = cultureInfo.Calendar.GetWeekOfYear(lastDateOfYear, cultureInfo.DateTimeFormat.CalendarWeekRule, dayOfWeek);

    var firstDayOfWeekDates = new List<DateTime>();
    firstDayOfWeekDates.Add(firstDate);

    var currentDate = firstDate;

    for (int i = 0; i < numberOfWeeksInYear; i++)
    {
        var weekLater = currentDate.AddDays(7);

        if (weekLater.Year == year)
        {
            currentDate = weekLater;
            firstDayOfWeekDates.Add(currentDate);
        }
    }

    return firstDayOfWeekDates;
}

您可以使用这样的控制台应用程序对此进行测试（将方法设为静态）：

static void Main(string[] args)
{
    var ci = new CultureInfo("en-GB");

    var dates = GetFirstDayOfWeekDates(ci, DateTime.Now.Year);

    foreach (var dt in dates)
    {
        Console.WriteLine("Date: " + dt.ToShortDateString());
    }

    Console.ReadLine();
}

它带来以下内容：

如果您还希望包括一周的结束日期，则可以通过添加一个名为WeekDate的新类来对其进行微调：

public class WeekDate
{
    public DateTime StartOfWeek { get; set; }
    public DateTime EndOfWeek { get; set; }
}

GetFirstDayOfWeekDates然后变为：

    public static IList<WeekDate> GetFirstDayOfWeekDates(CultureInfo cultureInfo, int year)
    {
        var lastDateOfYear = new DateTime(year, 12, 31);
        var firstDate = new DateTime(year, 1, 1);
        var dayOfWeek = cultureInfo.DateTimeFormat.FirstDayOfWeek;

        while (firstDate.DayOfWeek != dayOfWeek)
        {
            firstDate = firstDate.AddDays(1);
        }
        
        var numberOfWeeksInYear = cultureInfo.Calendar.GetWeekOfYear(lastDateOfYear, cultureInfo.DateTimeFormat.CalendarWeekRule, dayOfWeek);

        var firstDayOfWeekDates = new List<WeekDate>();
        firstDayOfWeekDates.Add(new WeekDate { StartOfWeek = firstDate, EndOfWeek = firstDate.AddDays(6) });

        var currentDate = firstDate;

        for (int i = 0; i < numberOfWeeksInYear; i++)
        {
            var weekLater = currentDate.AddDays(7);

            if (weekLater.Year == year)
            {
                currentDate = currentDate.AddDays(7);
                firstDayOfWeekDates.Add(new WeekDate { StartOfWeek = currentDate, EndOfWeek = currentDate.AddDays(6) });
            }
        }

        return firstDayOfWeekDates;
    }

哪个返回：

如何在C＃中获取年份的星期开始日期（星期一）和结束日期（星期日）列表

4 个答案: