How to retrieve data from database in asp.net using c#

Retrieve data from database table

using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;
using System.IO;

public partial class _Default : System.Web.UI.Page
{
    SqlCommand cmd = new SqlCommand();
    DataRow dr;
    protected void Page_Load(object sender, EventArgs e)
    {
        cmd.CommandText = "SELECT * FROM lab WHERE Regn_No ='"+Label1.Text+"'";
        cmd.Connection = conn;

      //  cmd.Parameters.Add("@Regn_No", SqlDbType.VarChar).Value = TextBox1.Text;
        SqlDataReader dr;
        dr = cmd.ExecuteReader();
        dr.Read();
     //   Label1.Text = dr[2].ToString();
        Label2.Text = dr[3].ToString();
        Label20.Text = dr[1].ToString();
        Label21.Text = dr[2].ToString();
        Label22.Text = dr[4].ToString();
        Label23.Text = dr[5].ToString();
        Label24.Text = dr[6].ToString();
        Label25.Text = dr[7].ToString();
        Label26.Text = dr[8].ToString();
        //GridView1.DataBind();
        dr.Close();
        //TextBox1.Text = "";
        //TextBox2.Text = "";
        //TextBox3.Text = "";
    }
}