public Form1()
        {
            InitializeComponent();
            List<A> list = new List<A>();
            list.Add(new A(10, "QQQ"));
            list.Add(new A(22, "WWW"));
            list.Add(new A(33, "EEE"));
            comboBox7.DataSource = list;
            comboBox7.DisplayMember = "Name";
            //foreach (var item in (List<A>)combo.DataSource)
            for (int i = 0; i < comboBox7.Items.Count; i++)
            {
                MessageBox.Show(comboBox7.Items[i].ToString());
            }
        }
    }


    class A
    {
        public A(int id, String name)
        {
            Id = id;
            Name = name;
        }
        public int Id { get; set; }
        public String Name { get; set; }
        public override string ToString()
        {
            return Name;
        }
    }