Roberto Brunetti - Exam Ref 70-485: Advanced Windows Store App Development Using C#

This objective covers how to:

In Windows Store apps, when users work on an app in the foreground, background apps cannot interact directly with them. In fact, due to the architecture of Microsoft Windows 8 and because of the application life-cycle management of Windows Store apps, only the foreground app has the focus and is in the running state; the user can choose two applications in the foreground using the snapped view. All the other background apps can be suspended and even terminated by the Windows Runtime. A suspended app cannot execute code, consume CPU cycles or network resources, or perform disk activity such as reading or writing files.

You can define a background task that runs in the background, however, even in a separate process from the owner app, and you can define background actions. When these actions need to alert users about their outcomes, they can use a toast. A background task can execute code even when the corresponding app is suspended, but it runs in an environment that is restricted and resource-managed. Moreover, background tasks receive only a limited amount of system resources.

You should use a background task to execute small pieces of code that require no user interaction. You can also use a background task to communicate with other apps via instant messaging, email, or Voice over IP (VoIP). Avoid using a background task to execute complex business logic or calculations because the amount of system resources available to background apps is limited. Complex background workloads consume battery power as well, reducing the overall efficiency and responsiveness of the system.