C# WinForms viele Comboboxen befüllen und auslesen

class ComboBoxGroup
    {
        public List<ComboBox> ComboBoxList { get; set; }
        public List<string> Items
        {
            set
            {
                foreach (ComboBox cbo in ComboBoxList)
                {
                    cbo.DataSource = value;
                }
            }
        }
        public int SelectedIndex
        {
            set
            {
                foreach(ComboBox cbo in ComboBoxList)
                {
                    cbo.SelectedIndex = value;
                }
            }
        }
        public ComboBoxGroup()
        {
            ComboBoxList = new List<ComboBox>();
        }
    }

  public partial class Form1 : Form
    {

        ComboBoxGroup group1 = new ComboBoxGroup();
        ComboBoxGroup group2 = new ComboBoxGroup();

        public Form1()
        {
            InitializeComponent();
            //Combo Boxen aus verschiedenen Tabs gruppieren
            //Gruppe1
            group1.ComboBoxList.Add(cboBoxT1);
            group1.ComboBoxList.Add(cboBoxT2);
            //Gruppe2
            group2.ComboBoxList.Add(cboBox2T1);
            group2.ComboBoxList.Add(cboBox2T2);
            //Controls befüllen
            group1.Items = new List<string> { "A", "B" };

        }

        private void cboBoxTX_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (((ComboBox)sender).SelectedItem.ToString() == "A")
            {
                group2.Items = new List<string> { "A1", "A2" };
                group2.SelectedIndex =0;
            }
            if (((ComboBox)sender).SelectedItem.ToString() == "B")
            {
                group2.Items = new List<string> { "B1", "B2" };
                group2.SelectedIndex = 1;
            }
        }
    }

    public class MultiControlState
    {
        public List<ComboBox> ControlList { get; set; } = new List<ComboBox>();
        private List<string> _itemList { get; set; } = new List<string>();

        public void Add(ComboBox inControl)
        {
            ControlList.Add(inControl);
            inControl.DataSource = _itemList;
            inControl.Tag = this;
        }

        private void SynchronizeControls(ComboBox inSender)
        {
            foreach (var tmpBox in ControlList.Where(inItem => inItem != inSender))
            {
                tmpBox.SelectedIndexChanged -= ComboBox_Changed;
                tmpBox.SelectedIndex = inSender?.SelectedIndex ?? 0;
                tmpBox.SelectedIndexChanged += ComboBox_Changed;
            }
        }

        private void ComboBox_Changed(object sender, EventArgs e)
        {
            SynchronizeControls(sender as ComboBox);
        }

        //von dir kopiert, da es sehr viel sinn macht und Entwickler faul sind.^^
        public List<string> Items
        {
            set
            {
                ControlList.ForEach(inItem => inItem.DataSource = value);
                _itemList = value;
            }
        }
    }