displaying user account data and then update into database

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ASP.NET

I am trying to update a user account, i mean when a user signed up and continue with its account than i wish that he is capable to Update its account with clicking update button, so i used SqlDataReader rd = rd.sqldatareader; command to retrive data from database, and displays these data into textboxs, and i am successed to do this when i run it. But problem is that when i run it and doing changes in textboxes and than click update button for update account it is not updating my account witout error....

my code of .cs file is below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;

public partial class updateaccount : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e) //for dsplay usr data in textboxes
    {
        SqlConnection con = new SqlConnection("server=.\\SQLEXPRESS; AttachDbFileName=|DataDirectory|\\Database.mdf; user instance=true; trusted_connection=yes");
        con.Open();
        SqlCommand cmd = new SqlCommand("SELECT * FROM signup WHERE id='"+(string)Session["User"]+"'",con);    //here Session user ='user id'
        SqlDataReader rd = cmd.ExecuteReader();
        
        if (rd.Read())
        {
             TextBox1.Text = rd.GetString(0).ToString();
             TextBox2.Text = rd.GetString(1).ToString();
             TextBox3.Text = rd.GetString(2).ToString();
             TextBox4.Text = rd.GetString(5).ToString();
             TextBox5.Text = rd.GetString(6).ToString();
             DropDownList1.SelectedValue = rd.GetString(7).ToString();
             TextBox6.Text = rd.GetString(8).ToString();
        }
        

    }

protected void Button1_Click(object sender, EventArgs e) //for updtng usr acount
    {
        SqlConnection con = new SqlConnection("server=.\\SQLEXPRESS; AttachDbFileName=|DataDirectory|\\Database.mdf; user instance=true; trusted_connection=yes");
        con.Open();
        SqlCommand cmd = new SqlCommand("UPDATE signup SET fn = '"+ this.TextBox1.Text + "', ln = '" + this.TextBox2.Text + "', emailid= '" + this.TextBox4.Text + "', address = '" + this.TextBox5.Text + "', scquestion = '" + this.DropDownList1.SelectedValue + "', answer = '"+ this.TextBox6.Text +"' WHERE id = '"+ (string)Session["User"] +"' ",con);
        SqlDataReader rd = cmd.ExecuteReader();
        con.Close();
        Label3.Text = "Update successfully";
    }
}      //this code not updating my account rather it Prints "Update successful"