private async void EditConference_Click(object sender, RoutedEventArgs e)
        {
            if (ConferencesBox.SelectedIndex >= 0)
            {
                var conference = await confCore.GetConferenceByIdAsync(int.Parse(ConferencesBox.SelectedValue.ToString()));

                Conference.AddEditConference newAddConferenceWindow = new Conference.AddEditConference(conference);
                newAddConferenceWindow.ShowDialog();
            }
            else
            {
                MessageBox.Show("Select conference");
            }
        }
 private void AddConference_Click(object sender, RoutedEventArgs e)
 {
     Conference.AddEditConference newAddConferenceWindow = new Conference.AddEditConference(null);
     newAddConferenceWindow.ShowDialog();
 }