private async void Cb_countries_SelectionChanged(object sender, SelectionChangedEventArgs e) {//select country try { if (cb_countries.SelectedIndex != -1) { dpnl_agent.IsEnabled = true; await FillCombo.fillAgentByCountry(cb_agents, (int)cb_countries.SelectedValue); } else { dpnl_agent.IsEnabled = false; cb_agents.SelectedIndex = -1; } await Search(); } catch (Exception ex) { HelpClass.ExceptionMessage(ex, this); } }