How to show database values on pageload in asp.net c#

In this article , I am going to show database value on textbox on pageload event.

protected void Page_Load(object sender, EventArgs e)

    {

       

        if (Session["username"] != null)

        {

      
      if (!IsPostBack)

            {

               Displayinformation();

            }

        }

    }

protected void displayinformation ()

    {

        try

        {

            string username = Session["username"].ToString();

            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString);

            con.Open();

            string newVariable = "select * from registration where Username ='" + username + "'";

            SqlCommand command = new SqlCommand(newVariable, con);

            SqlDataReader dr = command.ExecuteReader();

            if (dr.Read())

            {

                txtfirstname.Text = dr["firstname"].ToString();

                txtlastname.Text = dr["lastname"].ToString();

                ddlgender.Text = dr["gender"].ToString();

                txtemail.Text = dr["email"].ToString();

                txtdob.Text = dr["dob"].ToString();

                txtcurrentcity.Text = dr["currentcity"].ToString();

                ddlnation.Text = dr["nationality"].ToString();

                con.Close();

            }

        }

        catch (Exception ex)

        {

            Response.Write(ex.Message);

        }

    }