The Windows Phone OS applies tight control over which, if any, of the lock screen’s fields an app can modify. The user must grant permission to an app to allow it to change the lock screen background image. The user can do this either by appointing your app as the lock screen background image provider in the phone’s settings (see Figure 13.10) or by accepting a confirmation dialog the first time your app attempts to change the lock screen’s background image.
SetBackgroundAsync method of the custom
LockScreenService class demonstrates how to set ...