ApplicationBar

<phone:PhoneApplicationPage.ApplicationBar>

  <shell:ApplicationBar IsVisible="True">

    <shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="Won't work" Click="ApplicationBarIconButton_Click" />

  </shell:ApplicationBar>

</phone:PhoneApplicationPage.ApplicationBar>

private void ApplicationBarIconButton_Click(object sender, EventArgs e)

  {

    MessageBox.Show("This messagebox won't show!");

  }