get nth weekday of month in C#

Question

Possible Duplicate:
How do I determine if a given date is Nth weekday of the month?

How do i get the nth weekday of the month?

For ex.:

2nd Monday of "July 2010" = 07/12/2010.

Looking for a function like:

public DateTime GetNthWeekofMonth(DateTime date, int nthWeek, DayOfWeek dayofWeek)
{
//return the date of nth week of month
}

from the above, the parameters of the function will be ("Any Date in July 2010", 2, Monday).

Answer 1

One possible algorithm:

1. Start from the 1st of the month.
2. Move forward one day at a time until you get the Day of Week you're looking for.
3. Add (7 * N) to the date you're on to get the date you want.

Answer 2

Duplicate can be found here: http://stackoverflow.com/questions/288513/how-do-i-determine-if-a-given-date-is-nth-weekday-of-the-month

int d = date.Day; 
return date.DayOfWeek == dow && (d-1)/7 == (n-1); 

Answer 3

Use the following extension method:

///<summary>Gets the first week day following a date.</summary>
///<param name="date">The date.</param>
///<param name="dayOfWeek">The day of week to return.</param>
///<returns>The first dayOfWeek day following date, or date if it is on dayOfWeek.</returns>
public static DateTime Next(this DateTime date, DayOfWeek dayOfWeek) { 
    return date.AddDays((dayOfWeek < date.DayOfWeek ? 7 : 0) + dayOfWeek - date.DayOfWeek); 
}

You can then write

new DateTime(2010, 07, 01).Next(DayOfWeek.Monday).AddDays((2 - 1) * 7);

Or, as a function:

public DateTime GetNthWeekofMonth(DateTime date, int nthWeek, DayOfWeek dayofWeek) {
    return date.Next(dayOfWeek).AddDays((nthWeek - 1) * 7);
}

(I need to subtract one because date.Next(dayOfWeek) is already the first occurrence of that day)

Answer 4

IEnumerable<DateTime> WeekdaysFrom( DateTime start )
{
    DateTime weekday = start.Add( TimeSpan.FromDays(1) );
    while( weekday < DateTime.MaxValue.Subtract( TimeSpan.FromDays(1) ) )
    {
        while( weekday.DayOfWeek == DayOfWeek.Saturday || weekday.DayOfWeek == DayOfWeek.Sunday )
        {
            weekday.Add( TimeSpan.FromDays(1) );
        }
        yield return weekday;
    }
}

DateTime NthWeekday( DateTime month, int n )
{
    return WeekdaysFrom( new DateTime( month.year, month.month, 1 ) ).Skip(n-1).First();
}