TheAirline.Models.Airlines.Alliance.AddMember C# (CSharp) Method

        public void AddMember(AllianceMember airline)
        {
            Members.Add(airline);
            airline.Airline.AddAlliance(this);
        }

        private void btnCreate_Click(object sender, RoutedEventArgs e)
        {
            var alliance = new Alliance(
                GameObject.GetInstance().GameTime,
                txtName.Text.Trim(),
                (Airport)cbHeadquarter.SelectedItem);
            alliance.Logo = logoPath;
            alliance.AddMember(
                new AllianceMember(GameObject.GetInstance().HumanAirline, GameObject.GetInstance().GameTime));

            Alliances.AddAlliance(alliance);

            var tab_main = UIHelpers.FindChild<TabControl>(Tag as Page, "tabMenu");

            if (tab_main != null)
            {
                TabItem matchingItem =
                    tab_main.Items.Cast<TabItem>().Where(item => item.Tag.ToString() == "Alliances").FirstOrDefault();

                //matchingItem.IsSelected = true;
                tab_main.SelectedItem = matchingItem;
            }
        }