protected void loginButton_Click(object sender, EventArgs e)
        {
            string centerCode = centerCodeTextBox.Text;
            string password   = passwordTextBox.Text;
            string enPassword = EncryptSHA512Managed(password);

            if (centerManager.IsCenterCodeAndPasswordExists(centerCode, enPassword))
            {
                Session["CenterId"] = centerManager.GetCenterId();
                int centerId = centerManager.GetCenterId();
                int thanaId  = centerManager.GetThanaId(centerId);
                Session["DistrictId"] = centerManager.GetDistrictId(thanaId);
                Response.Redirect("HomeCenter.aspx");
            }
            else
            {
                megLabel.Text = "Wrong centercode and password!";
            }
        }