private void cmbRoom_SelectionChanged(object sender, SelectionChangedEventArgs e) { cmbActivity.Items.Clear(); List <DataTypes> roomActivityCombo = new List <DataTypes>(); roomActivityCombo = viewModel.GetRoomActivityCombo(); for (int i = 0; i < roomActivityCombo.Count; i++) { if (roomActivityCombo[i].Room.ToString() == cmbRoom.SelectedValue.ToString()) { cmbActivity.Items.Add(roomActivityCombo[i].Activity); } } }