private void bBeginRollCall_Click(object sender, RoutedEventArgs e)
 {
     if (!MainViewModel.RollCallService.RollCallActive)
     {
         Windows.RollCallView rcv = new Windows.RollCallView(MainViewModel);
         rcv.Show();
     }
 }
 private void bBeginRollCall_Click(object sender, RoutedEventArgs e)
 {
     if (!MainViewModel.RollCallService.RollCallActive)
     {
         Windows.RollCallView rcv = new Windows.RollCallView(MainViewModel);
         rcv.Show();
     }
 }