The property of GridView1.HasRows is true and after assigning
GridView.DataSource=reader, it does not display any records in the
GirdView.

I am i missing out something? Here is the code:
protected void Button1_Click(object sender, EventArgs e)
   {
int AtmtransId=-1;
           if (Session["CustomerId"]!=null)

AtmtransId=DataAccessLayer.ATMManager.getATMTransactionsID(Session["CustomerId"].ToString(),AccNamesList.SelectedItem.Text);
       string Query = "SELECT atmtrans_date AS Date,atmtrans_branch
AS Branch,atmtrans_type AS Type,atmtrans_amount AS Amount FROM
ATM_Transactions WHERE atmtrans_id=@ATMTRANSID";
       SqlConnection sqlconnection = new SqlConnection(@"Data Source=.
\SQLEXPRESS;AttachDbFilename=|DataDirectory|\BankingDb.mdf;Integrated
Security=True;User Instance=True");
       SqlCommand cmd = new SqlCommand(Query,sqlconnection);
       cmd.Parameters.AddWithValue("@ATMTRANSID",AtmtransId);
       sqlconnection.Open();
       SqlDataReader reader=cmd.ExecuteReader();
       sqlconnection.Close();
       GridView1.DataSource=reader;
}