DateTime.DaysInMonth

I stumbled upon this yesterday and thought it was worth publicising a bit.


I'm writing a tidgy little app that will take a load of data about our press releases out of one of our databases and turn into flat HTML files. It needs to write separate files for years and months - years are easy as it's just a for loop, and months are also a for loop, but I need to know the end date for each month so I can create the appropriate SQL query. I'd written a switch block to calculate the last day of the month:


for (int i = 1; i < 13; i++)
{
    DateTime startDate = new DateTime(int.Parse(year), i, 1, 0, 0, 0);
    DateTime endDate;


    switch (i)
    {
        case 9, 4, 6, 11:
            endDate = new DateTime(int.Parse(year), i, 30, 23, 59, 59);
            break;
        case 2:

            endDate = new DateTime(int.Parse(year), i, 28, 23, 59, 59);

            // TODO: Leap years

            break;

        default:

            endDate = new DateTime(int.Parse(year), i, 31, 23, 59, 59);

            break;

     }
}

But further down in my code, I was doing something else with the DateTime class and I spotted it has a DaysInMonth function. You give it a year and a month (both ints), and it calculates the number of days in the month for you, and deals with the leap years that I hadn't got round to doing. Which means I can collapse my for down to:

for (int i = 1; i < 13; i++)

{

    DateTime startDate = new DateTime(int.Parse(year), i, 1, 0, 0, 0);

    DateTime endDate = new DateTime(int.Parse(year), DateTime.DaysInMonth(int.Parse(year), i), 30, 23, 59, 59);

}

Smaller code for the win!


EDIT: I just looked DaysInMonth up on MSDN and I'm surprised to discover it's been in the Framework since .NET 1.0!