private async void SaveChangesAsync(object sender, RoutedEventArgs e)
        {
            var dialog = new MessageDialog("Are you sure?");

            dialog.Title = "Really?";
            dialog.Commands.Add(new UICommand {
                Label = "Ok", Id = 0
            });
            dialog.Commands.Add(new UICommand {
                Label = "Cancel", Id = 1
            });
            var res = await dialog.ShowAsync();

            if ((int)res.Id == 1)
            {
                return;
            }
            if (ViewModel.SelectedDeparture == null)
            {
                ViewModel.SelectedDeparture = new Departure();
            }
            ViewModel.SelectedDeparture.Crew   = ViewModel.Crews.SingleOrDefault(c => c.ToString() == Crews.SelectedItem.ToString());
            ViewModel.SelectedDeparture.Plane  = ViewModel.Planes.SingleOrDefault(c => c.ToString() == Planes.SelectedItem.ToString());
            ViewModel.SelectedDeparture.Flight = ViewModel.Flights.SingleOrDefault(c => c.ToString() == Flights.SelectedItem.ToString());
            try
            {
                ViewModel.SelectedDeparture.Date = DateTime.Parse(Date.ToString());
            }
            catch (Exception)
            { }

            if (ViewModel.SelectedDeparture != null)
            {
                ViewModel.UpdateDeparture();
            }
            else
            {
                ViewModel.AddDeparture();
            }
        }