Coding the Trial Experience with Windows Phone 8

A couple of days ago I decided to make an app to access the Sinclair Infoseek service at World of Spectrum.  It’s going well so far, I have the basic search up and running, along with a display of the results.

I intend to add other features as and when I think of them. Current planned features include:

• Favourites: Save your favourite searches
• SkyDrive: Save the searches to SkyDrive
• SkyDrive 2: When you have found an interesting game, you can pick the .tap/.tzx etc to upload to your SkyDrive account so that you can load it up in a ZX Spectrum emulator.  On Windows Phone I use MetroSpec. I might even attempt to open the game in MetroSpec directly from my app.
• Save/Load Screens: Save and Load loading screens and in-game screens. Allow zooming etc.
• A page that gets a random infoseek entry (maybe 30-50 at a time), so that you can browse through games that you may have never seen before, :)
• More stuff that I cannot remember (why is it that I wake up at 3am with great ideas, then forget them by the time I get up in the morning…)

Now, back on-topic…

I would like to disable some features until the user has purchased the app (at the cheapest price that the Windows Phone App Store allows), so I had to be able to allow users to trial the app. I was worried that it might be a complicated process, but found that it was very, very easy.

Here are the steps I used:

1. Add this line to your App.xaml.cs file

   using Microsoft.Phone.Marketplace;

2. In the App class, declare the a local static variable which used the LicenseInformation class to determine if the app is running under a trial license or not

        private static LicenseInformation _licenseInfo = new LicenseInformation();

3. Now you need a variable to cache whether the app is in Trial mode or not, so place this in yourApp.xaml.cs

           private static bool _isTrial = true;
           public bool IsTrial
           {
               get
               {
                   return _isTrial;
               }
           }

4. Now for a method for checking the license. Again, this should go in App.xaml.cs

           private void CheckLicense()
           {
               // this displays a dialog so that we can simulate trial mode being on or off. 
   #if DEBUG
               string message = "Press 'OK' to simulate trial mode. Press 'Cancel' to run the application in normal mode.";
               if (MessageBox.Show(message, "Debug Trial",
                    MessageBoxButton.OKCancel) == MessageBoxResult.OK)
               {
                   _isTrial = true;
               }
               else
               {
                   _isTrial = false;
               }
   #else
               _isTrial = _licenseInfo.IsTrial();
   #endif
           }

5. We must check the trial status whenever the app is started or whenever it resumes from a sleeping state.  Once again, this code goes in App.xaml.cs

   private void Application_Launching(object sender, LaunchingEventArgs e)
           {
               CheckLicense();
           }
           private void Application_Activated(object sender, ActivatedEventArgs e)
           {
               CheckLicense();
           }

6. To use this in your app, whenever you have code that should not be run when the user is in trial mode, you just use

   if ((Application.Current as App).IsTrial)
   {
       // Do this if app is in trial mode, the usual thing would be to inform the user
       // that the feature is no available in the trial and ask them to purchase the 
       // full app from the store.
   }
   else
   {
       // Do this if the app is *not* in trial mode
   }

7. That’s all there is to it, easy huh. :)