private void btnUpdate_Click(object sender, EventArgs e)
        {
            BillEntity en = new BillEntity();
            BillRepo   re = new BillRepo();

            en.Id        = txtTestNo.Text;
            en.Name      = txtPatient.Text;
            en.Date      = dtpDate.Value.ToString("yyyy-MM-dd");
            en.Age       = int.Parse(txtAge.Text);
            en.Sex       = txtSex.Text;
            en.Time      = dtpTime.Value.ToString("hh:mm tt");
            en.Reference = txtReference.Text;

            re.UpdateOrders(en);
        }
        private void View(string no)
        {
            BillRepo   re = new BillRepo();
            BillEntity en = re.Credentials(no);

            txtPatient.Text   = en.Name;
            txtAge.Text       = en.Age.ToString();
            txtSex.Text       = en.Sex;
            txtReference.Text = en.Reference;
            txtTests.Text     = en.Tests;
            txtPrice.Text     = en.Price;
            txtTotal.Text     = en.Total;
            txtDiscount.Text  = en.Discount;
            dtpDate.Text      = en.Date;
            dtpTime.Text      = en.Time;
        }