How to display data in datalist in c#?

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

public partial class displaydata : System.Web.UI.Page
{
    SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\gtu.mdf;Integrated Security=True;User Instance=True");
    protected void Page_Load(object sender, EventArgs e)
    {

        con.Open();
        SqlCommand cmd = con.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = "select * from table_name";
        cmd.ExecuteNonQuery();
        DataTable dt = new DataTable();
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        da.Fill(dt);
        d1.DataSource = dt;
        d1.DataBind();
    }
}


////display.aspx - source page

<asp:DataList ID="d1" runat="server" RepeatColumns="3">
    <HeaderTemplate>
        <table>
            <tr>
                <td style="background-color: White;">
                    Name</td>
            </tr>
    </HeaderTemplate>
    <ItemTemplate>
        <tr>
            <td>
                <center>
                    <span style="color: #6b633f">
                        <%#Eval("column_name") %>
                    </span>
                </center>
            </td>
        </tr>
    </ItemTemplate>
    <FooterTemplate>
        </table>
    </FooterTemplate>
</asp:DataList>