<form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
            <Columns>
                <asp:BoundField HeaderText="Name" DataField="S2" />
                <asp:BoundField HeaderText="City" DataField="S3" />
                <asp:BoundField HeaderText="City" DataField="S4" />
            </Columns>
        </asp:GridView>
    </div>
    </form>

public partial class _Default : System.Web.UI.Page 
{
 
    private BindingList<TestClass> mono = new BindingList<TestClass>();
    protected void Page_Load(object sender, EventArgs e)
    {
        mono.Add(new TestClass("1","a","b","c"));
        mono.Add(new TestClass("2", "aa", "bb", "cc"));
        mono.Add(new TestClass("3", "aaa", "bbb", "ccc"));
        mono.Add(new TestClass("4", "aaaa", "bbbb", "cccc"));
        mono.Add(new TestClass("5", "aaaaa", "bbbbb", "ccccc"));
        
        GridView1.DataSource = mono;
        GridView1.DataBind();
    }
}