Asp.net with c# sqlserver2005

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ASP.NET

using System;
using System.Collections;
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;
namespace photoshops
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        SqlConnection conn = new SqlConnection();
        protected void Page_Load(object sender, EventArgs e)
        {
            conn.ConnectionString
              = @"Data Source=DEVI\SQLEXPRESS; Initial Catalog =cat; Integrated Security=SSPI";
            Load_GridData(); // call method below
        }
        void Load_GridData()
        {
            conn.Open(); // open the connection 
            SqlDataAdapter Sqa = new SqlDataAdapter("select * from tblphotosettings", conn);
            DataSet ds = new DataSet();
            Sqa.Fill(ds);  // fill the dataset 
            GridView1.DataSource = ds.Tables[0]; // give data to GridView
            conn.Close();
        }
        protected void Button1_Click(object sender, EventArgs e)
        {
            string strText = TextBox1.Text;
            SqlDataAdapter Sqa = new SqlDataAdapter("select * from tblphotosettings where BillNo= " + strText + "", conn);
        }
    }
}

i have enter a textbox in customer bill number and then click the button display image customer record in a gridview.... How to change in my code.. because i am begineer... can you post the code