datetime - In .net, knowing the week number how can I get the weekdays date?

Question

I want to create a function in C# which for a week number will return me the days, in that week.

For instance for week number 40, how can I get the days: 4/10, 5/10, 6/10, 7/10, 8/10, 9/10, 10/10.

Thank you in advance!

Answer 1

I think this should do what you want:

    public static DateTime[] WeekDays(int Year, int WeekNumber)
    {
        DateTime start = new DateTime(Year, 1, 1).AddDays(7 * WeekNumber);
        start = start.AddDays(-((int)start.DayOfWeek));
        return Enumerable.Range(0, 7).Select(num => start.AddDays(num)).ToArray();
    }

Although I treat Sunday as first day of week, if you want Monday as first day change range from (0,7) to (1,7).

If you want to conform the ISO standard, I think this should work:

    public static DateTime[] WeekDays(int Year, int WeekNumber)
    {
        DateTime start = new DateTime(Year, 1, 4);
        start = start.AddDays(-((int)start.DayOfWeek));
        start = start.AddDays(7 * (WeekNumber - 1));
        return Enumerable.Range(0, 7).Select(num => start.AddDays(num)).ToArray();
    }