Using custom message box in windows phone app

custom_message_box.cs

CustomMessageBox msg=new CustomMessageBox()
{
    Caption="Location Settings",
    Message="Location seems to be disabled on your device. Do your want to change your settings?",
    LeftButtonContent="yes",
    RightButtonContent="no"
};
msg.Dismissed += (s1, e1) =>
{
    switch (e1.Result)
    {
        case CustomMessageBoxResult.LeftButton:
            // Do something.
            break;
        case CustomMessageBoxResult.RightButton:
             NavigationService.Navigate(new Uri("/SelectCircle.xaml", UriKind.Relative));
            break;
        case CustomMessageBoxResult.None:
            // Do something.
            break;
        default:
            break;
    }
};
msg.Show();