protected void dueAmountPayButton_Click(object sender, EventArgs e)
        {
            BillManager billManager = new BillManager();
            string      amount      = amountTextBox.Value.ToString().Trim();

            if (amount != "")
            {
                string billNo = ViewState["BillNo"].ToString();
                bool   isPaid = billManager.IsBillPaid(billNo);
                if (isPaid == true)
                {
                    testTypeSuccessfullAlartLabel.Text = "Bill already Paid.";

                    testTypeSuccessfullDiv.Visible = true;
                }
                else
                {
                    int rowAffected = billManager.UpdateBillStatus(billNo);

                    if (rowAffected > 0)
                    {
                        testTypeSuccessfullAlartLabel.Text = "Bill Successfully paid.";

                        testTypeSuccessfullDiv.Visible = true;
                    }
                }
            }
        }