private void button4_Click(object sender, EventArgs e)
{
string station = (string)stationsList.SelectedItem;
string city = (string)citiesList.SelectedItem;
Station selectedStation = findSelectedStation(station);
Stopwatch stopwatch = Stopwatch.StartNew();
string informations = client.GetInformations(selectedStation.Number, city);
stopwatch.Stop();
label8.Text = "Execution time of GetInformations: " + stopwatch.ElapsedMilliseconds + "ms";
label8.Visible = true;
label7.Text = informations;
}