async void Handle_SelectionChanged(object sender, Syncfusion.XForms.ComboBox.SelectionChangedEventArgs e) { var selectedCustomer = customers.Find(cust => cust.Value == customerComboBox.Text); var content = await CommonFunction.CallWebService(0, null, Ultis.Settings.SessionBaseURI, ControllerUtil.getCustomerDetail(selectedCustomer.Key), this); clsResponse response = JsonConvert.DeserializeObject <clsResponse>(content); if (response != null) { pickupList.Clear(); comboBoxList = JObject.Parse(content)["Result"].ToObject <Lists>(); foreach (clsKeyValue pickUp in comboBoxList.PickupList) { pickupList.Add(pickUp.Value); } pickUpComboBox.ComboBoxSource = null; pickUpComboBox.ComboBoxSource = pickupList; } }