People who starts learning any programing language have the problem that how they can find out no. of days in a particular month of a year. Sometimes it has been given as assignments to them and sometimes our real world programming creates the situation where we have to do the same, recently I was surfing a forum site and stop by on the same question so thought to write an article about it.

I will write the function in two ways first the traditional approach and second will implement Linq in that

First: The traditional implementation:

Create a Function which will return an integer value of times the particular day will occur in a particular month of the year

/// <summary>

/// Count number of times day will fall in a month of a year

/// </summary>

/// <param name="year">Year in which the month will fall</param>

/// <param name="month">Month for which we need to count the no of days</param>

/// <param name="dayOfWeek">day of week which we wnt to count</param>

/// <returns>Number of times the day will fall in that month</returns>

static int NumberOfParticularDaysInMonth(int year, int month, DayOfWeek dayOfWeek)

{

//create a variable to start from date i.e. 1st of that month in thta year which has passed as arrgument

DateTime startDate = new DateTime(year, month, 1);

//use the function of DateTime class which will return the no of days in thta particular month

int days = DateTime.DaysInMonth(startDate.Year, startDate.Month);

//create and initalize a variable with 0 which will hold no of occurnces in that month

int weekDayCount = 0;

//create a loop to count the number of occurncess of that day

for (int day = 0; day < days; ++day)

{

//add days to the start date and check its day of week is what we are counting for if yes add 1 to our variable else add 0

weekDayCount += startDate.AddDays(day).DayOfWeek == dayOfWeek ? 1 : 0;

}

//return the count variable

return weekDayCount;

}

Now what we need is just to call above function will be like this

int CountDayOfWeekInMonth = NumberOfParticularDaysInMonth(2010, 9, DayOfWeek.Friday);

The Linq Implementation of the same function will go like this

/// <summary>

/// Count number of times day will fall in a month of a year

/// </summary>

/// <param name="year">Year in which the month will fall</param>

/// <param name="month">Month for which we need to count the no of days</param>

/// <param name="dayOfWeek">day of week which we wnt to count</param>

/// <returns>Number of times the day will fall in that month</returns>

static int NumberOfParticularDaysInMonth(int year, int month, DayOfWeek dayOfWeek)

{

//create a variable to start from date i.e. 1st of that month in thta year which has passed as arrgument

DateTime startDate = new DateTime(year, month, 1);

//use the function of DateTime class which will return the no of days in thta particular month

int days = startDate.AddMonths(1).Subtract(startDate).Days;

//use Linq to get the no of occurance of that day

int weekdaycount = Enumerable.Range(1, days)

.Select(item => new DateTime(year, month, item))

.Where(date => date.DayOfWeek == dayOfWeek)

.Count();

//return the count variable

return weekdaycount;

}

Now you can call this above function using the following statement

int CountDayOfWeekInMonth = NumberOfParticularDaysInMonth(2010, 9, DayOfWeek.Friday);