Your application can be opened by user from "Suspended" state. When doing it "OnResuming" event handler is used. In "App.xaml.cs" class:
public App()
{
this.InitializeComponent();
this.Suspending += OnSuspending;
//Handle resuming operation:
this.Resuming += App_Resuming;
}
private void App_Resuming(object sender, object e)
{
//Do some operation connected with app resuming for instance refresh data
}