Recently someone challenged me to write a server-side method for finding the current season and changing a style sheet accordingly.

The first step is deciding how to differentiate the seasons. I figured to use the day of the year so that astronomically Spring begins on March 21^st, the 80^th day of the year. Summer begins on the 172^nd day, Autumn, the 266^th and Winter the 355^th. Of course, on a leap year add one day to each, 81, 173, 267 and 356.

Now to find the day of the year use the DayOfYear property. Also, use the IsLeapYear property to take a day away on leap year if the current day is after February 28^th (the 59^th day of the year). This is easily done by converting the bool IsLeapYear to an Int32 giving a 0 during non-leap years and 1 during leap year.
int doy = DateTime.Now.DayOfYear - Convert.ToInt32((DateTime.IsLeapYear(DateTime.Now.Year)) && DateTime.Now.DayOfYear > 59);

Then find the current season using a few nested ternary operators (I like ternary operators)
string currentSeason = String.Format("{0}.css",((doy < 80 || doy >= 355) ? "winter" : ((doy >= 80 && doy < 172) ? "spring" : ((doy >= 172 && doy < 266) ? "summer" : "fall"))));

I use this in the head of my MasterPage:
<link rel="Stylesheet" runat="server" id="seasonSheet" type="text/css" />

So all I have to do to add the correct style sheet for the current season is this:
seasonSheet.Attributes.Add("href",currentSeason);

Now a stylesheet named spring.css, summer.css, fall.css or winter.css will be added to your rendered MasterPage.

I hope you’ve found this helpful.

This entry was posted on 28Dec09 @ 1518 and is filed under ASP.NET, C#. You can follow any responses to this entry through the RSS 2.0 feed. You can this page, leave a response or trackback from your own site.