private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            string cityname = (ComboCity.SelectedItem as ComboBoxItem).Content.ToString();
            conectionc.conection_database(cityname, 1);

            Backgroundc.backg = cityname;
            conectionc.conection_database(cityname, 0);

            // jump into new window
               Window1 winweather = new Window1();
               winweather.ShowDialog();
               //MainWindow winm = new MainWindow();
               //winm.Close();
              //*-----------------
        }
        private void Application_Startup(object sender, StartupEventArgs e)
        {
            //add some bootstrap or startup logic

            string city = conectionc.retrieve_data() ;
            if (city == "vacio")
            {
                //LoginWindow login = new LoginWindow();
                //login.Show();
                MainWindow mainView = new MainWindow();
                mainView.ShowDialog();

            }
            else
            {
                Backgroundc.backg = city;
                Window1 winweather = new Window1();
                winweather.ShowDialog();
            }
        }