public partial class Form4 : Form
    {
        private BindingList<test1> bl = new BindingList<test1>();
        public static test2[] values = { new test2("none"), new test2("one"), new test2("two") };
        public Form4()
        {
            InitializeComponent();

            //bl.Add(new test1());

            dataGridView1.AutoGenerateColumns = false;
            dataGridView1.AutoSize = true;
            dataGridView1.DataSource = bl;
            dataGridView1.Columns.AddRange(getColumn());


        }
        private DataGridViewColumn getColumn()
        {
            var combo = new DataGridViewComboBoxColumn();
            combo.DataSource = values;
            combo.DataPropertyName = "t2";
            combo.DisplayMember = "s";
            combo.ValueMember = "Value";
            return combo;
        }
    }

    public class test1
    {
        private test2 _t2;

        public test2 t2
        {
            get
            {
                return _t2;
            }
            set
            {
                _t2 = value;
            }
        }

        public test1(test2 t2)
        {
            this.t2 = t2;
        }

        public test1()
        {
        }
    }

    public class test2
    {
        public string s { get; set; }

        public test2 Value {
            get { return this; }
        }

        public test2(string s = "none")
        {
            this.s = s;
        }
    }