Windows Phone 7 : Sensors - Displaying Sunset and Sunrise

1. Problem

Your aim is to obtain an application that is able to tell the user what time the sun will rise and set today in the user's location.

2. Solution

There are several ways to find out the time of sunrise and sunset (for example, through web services, libraries, and complex calculations). This recipe shows how to access and use a certain property in order to explore the potential of Location Services. There are several ways to calculate the times from latitude and longitude values, and we will let you choose which best suits your needs.

3. How It Works

You will use information about the user's position, obtained from the device, to calculate the time of sunrise and sunset, simulating with a helper class the behavior of a service to calculate them

4. The Code

To start writing code for this recipe we need two members field:

GeoCoordinateWatcher geo = new GeoCoordinateWatcher();
                SuntimesHelper ssc = new SuntimesHelper();

SuntimesHelper is a class written by us, whose code is based on algorithms that are easily available on the Internet. This class exposes two methods, called GetSunRise and GetSunSet, as you can see in Figure 1.

Figure 1. Class diagram of SuntimesHelper

void geo_PositionChanged(object sender, GeoPositionChangedEventArgs<GeoCoordinate> e)
{
            if (!e.Position.Location.IsUnknown)
            {
                bool isSunrise = false;
                bool isSunset = false;

                DateTime sunrise = SuntimesHelper.GetSunRise(e.Position.Location.Latitude,
e.Position.Location.Longitude, DateTime.Now, out isSunrise);
DateTime sunset = SuntimesHelper.GetSunSet(e.Position.Location.Latitude,
e.Position.Location.Longitude, DateTime.Now, out isSunset);
geo.Stop()
           }
}

					  

It is important when working with the position to point out that the applications used for localizing consume battery power. Although we may sound repetitive, it is important to provide the best possible user interaction in our applications. Therefore, remember to stop the use of GeoCoordinateWatcher when you don't need it anymore.

5. Usage