ตัวแปรในการ Connect DataBase .. Error 1 The name 'conn' does not exist in the current context

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Web.Configuration;


public partial class datagrid : System.Web.UI.Page
{
    private SqlConnection conn;

    protected void Page_Load(object sender, EventArgs e)
    {
        string str;
        str = WebConfigurationManager.ConnectionStrings["connDB"].ConnectionString;
        conn = new SqlConnection(str);
        conn.Open();
        if (!Page.IsPostBack)
        {
            BindData();
        }
        
    }
    protected void BindData()
    {
        string strsql = "select * From tbl_customer";
        SqlCommand com = new SqlCommand(strsql, conn);
        SqlDataReader dtReader;
        dtReader = com.ExecuteReader();
        myGridView.DataSource = dtReader;
        myGridView.DataBind();
        dtReader.Close();
        dtReader = null;
    }  
}