Use IsFirstRun to determine whether you need to perform any one-time initialization operations the first time your application runs.
Do not assume that a IsFirstRun setting of true indicates that this instance of an application is the first one to show its user interface to the user. Due to the way the system schedules processes, one instance of the application may have its IsFirstRun property set to true, but another instance may be the first to render on the screen. The value of this property is reset whenever the user upgrades from one version to the next. If you want to perform an operation only the very first time any version of the application is run, you will need to perform an additional test, such as checking for the existence of a file you created the first time, or storing a flag using Application Settings.