update getdatatable  to this   . This doesnt take care of paging right now , but we can go to that on next level.

[WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public s_GridResult GetDataTable(string sidx, string sord, int page, int pagesize)
        {
            int startindex = (page - 1) * pagesize;
            int endindex = page * pagesize;
            string sql = @" WITH PAGED_CUSTOMERS AS
                      {
                          SELECT BookID,BookName
                          ROW_NUMBER() OVER(ORDER BY " + sidx + @" " + sord + @") AS ROWNUMBER
                          FROM BOOKS}";
            DataTable dt = new DataTable();
            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["Data Source=.;Initial Catalog=library;Integrated Security=True"].ConnectionString);
            SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
            var rows = adapter.Fill(dt);
            s_GridResult result = new s_GridResult();
            List<s_RowData> rowsadded = new List<s_RowData>();
            int idx = 1;
            foreach (DataRow row in dt.Rows)
            {
                  s_RowData newrow = new s_RowData();
                  newrow.id = idx++;
                  newrow.cell = new string[2];  //total number of columns
                  newrow.cell[0] = row[0].ToString();
                  newrow.cell[1] = row[1].ToString();
                  rowsadded.Add(newrow);
            }
            result.rows = rowsadded.ToArray();
            result.page = page;
            result.total = dt.Rows.Count;
            result.record = rowsadded.Count;
            return result;
        }