How to display data from database into textbox, and update it

Question

I can display my data in my textbox, dropdownlist after retrieve data from sql database, but when i proceed with my update button, the information edited in the textbox or d

Answer 1

The answer is .IsPostBack as suggested by @Kundan Singh Chouhan. Just to add to it, move your code into a separate method from Page_Load

private void PopulateFields()
{
  using(SqlConnection con1 = new SqlConnection("Data Source=USER-PC;Initial Catalog=webservice_database;Integrated Security=True"))
  {
    DataTable dt = new DataTable();
    con1.Open();
    SqlDataReader myReader = null;  
    SqlCommand myCommand = new SqlCommand("select * from customer_registration where username='" + Session["username"] + "'", con1);

    myReader = myCommand.ExecuteReader();

    while (myReader.Read())
    {
        TextBoxPassword.Text = (myReader["password"].ToString());
        TextBoxRPassword.Text = (myReader["retypepassword"].ToString());
        DropDownListGender.SelectedItem.Text = (myReader["gender"].ToString());
        DropDownListMonth.Text = (myReader["birth"].ToString());
        DropDownListYear.Text = (myReader["birth"].ToString());
        TextBoxAddress.Text = (myReader["address"].ToString());
        TextBoxCity.Text = (myReader["city"].ToString());
        DropDownListCountry.SelectedItem.Text = (myReader["country"].ToString());
        TextBoxPostcode.Text = (myReader["postcode"].ToString());
        TextBoxEmail.Text = (myReader["email"].ToString());
        TextBoxCarno.Text = (myReader["carno"].ToString());
    }
    con1.Close();
  }//end using
}

Then call it in your Page_Load

protected void Page_Load(object sender, EventArgs e)
{

    if(!Page.IsPostBack)
    {
       PopulateFields();
    }
}