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Be aware that Sections 4.8 and 4.9 of the Store certification requirements apply here, where you need to
ensure that the user enters credentials for each purchase and that each transaction meets the PCI Data
Security Standards.
With this custom commerce option, you’re pretty much on your own where all the details are
concerned, including UI—the Windows Store API itself doesn’t provide for extensibility of its own
mechanisms. You might draw from The in-app purchase user experience for a customer topic in the
documentation to understand the flow, and you may also be able to find a third-party solution that
provides an app control along with the backend commerce services.
Note that although the Windows Store does not presently support consumable in-app purchases,
you can certainly implement this with your own commerce scheme. Doing so will also avoid the
100-item limit imposed by the Windows Store mechanisms.
The Windows Store APIs
Now that you’ve likely decided on a course for your app, let’s see how you use the Windows Store APIs
to accomplish those ends. These are found in the Windows.ApplicationModel.Store namespace; all
objects referred to in this section are contained in this namespace unless noted. 80
First, know that basic licensing and trial enforcement comes for free: the app doesn’t actually need to
do anything at all! A user cannot acquire your app without going through the Store, and even if he did
manage to, he’d have to have a developer license to install and run it. Furthermore, because the Store
automatically tracks trial periods for apps, Windows will simply not launch an app once the trial is
expired. Instead, Windows will redirect the user to the product’s page in the Store where the user can
purchase a full license.
An app can also set the expiration time of a license—not just for trials but the full app. This could be
useful for apps that aren’t valid or useful after a given date, such as event registration (conferences,
meetings, etc.) or time-limited demos. Think about it, though: if the user has gone to the trouble of
acquiring the app in the first place, do you really want to go and disable it? Far better, I imagine, is to
maintain the usefulness of the app in some way. With event registration, for example, there are
probably more events in the future that you could provide information about and perhaps open up
registration at the appropriate time. Again, the user has the app already and must have had some intent
in launching it even after it’s expired—so can you leverage that intent in some way? It’s a good question
to ask.
As noted before, apps can enforce a secondary licensing scheme if desired. Here it would ask the user
for a separate registration or a separately acquired license key of some sort. Again, Windows does not
offer an API for this but will not block schemes of your own.
80 To make a note, the Windows.ApplicationModel.Package class also provides a few details about the installed app
package. Usage is simple, and you can refer to the App package information sample for more.
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