ช่วยดูโค้ดหน้าล็อกอินทีค่ะ พอลองล็อกอินที่ไม่มีในฐานข้อมูลก็ขึ้นฟ้อง Object reference not set to an instance of an object. อ่ะ

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.Web.Configuration;
using System.IO;
using System.Text;


public partial class login : System.Web.UI.Page
{
    string strConn = WebConfigurationManager.ConnectionStrings["myConn"].ConnectionString;
    SqlConnection myConn = new SqlConnection(WebConfigurationManager.ConnectionStrings["myConn"].ConnectionString);

    string sqlSelect;

    protected void Page_Load(object sender, EventArgs e)
    {
       
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        sqlSelect = " SELECT StudentUser,StudentPsw FROM Tb_Student WHERE  (Tb_Student.StudentUser='" + txtUserName.Text + "')";
        sqlSelect += " AND (Tb_Student.StudentPsw ='" + txtPassWord.Text + "')";

        SqlDataAdapter adap = new SqlDataAdapter(sqlSelect, myConn);
        DataSet ds = new DataSet();
        adap.Fill(ds, "data");

        int count = ds.Tables["data"].Rows.Count;
        string[] user = new string[count];
        string[] pass = new string[count];

        if (count == 0)
        {
           
            lblAlert.Text = "ไม่พบข้อมูลในฐานข้อมูล";
            Session.RemoveAll();
        }
        if (count != 0)
        {
            for (int i = 0; i <= count - 1; i++)
            {
                user[i] = ds.Tables["data"].Rows[i].ItemArray[1].ToString();
               
                // เก็บ session
                Session["user"] = user[i]; 
                Session["Login"] = "ok";
            }
         }
            Response.Redirect("StuMain.aspx");
        }
        
    }