protected void gvBookList_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
            try
            {
                bookTable = (List <BookBO>)Session[Common.sessionBookList];
                BookBL bookBL = new BookBL();

                bookTable            = bookBL.DeleteById(gvBookList.DataKeys[e.RowIndex].Values[0], bookTable);
                Session["BooksList"] = bookTable;
                FillGrid();
                lblSuccessMessage.Text = Common.msgDeleteSuccess;
            }
            catch (Exception ex)
            {
                // log exception
                lblErrorMessage.Text = Common.msgDeleteFailure;
            }
        }