StringBuilder str = new StringBuilder();

                var res = new ResParameter() { code = ResponseCode.exception };

                var result = from isbn in dt.AsEnumerable()

                             group isbn by isbn.Field<string>("isbn") into grp

                             where grp.Count() >

                             select grp.Key;

                if (result.Count() > )

                {

                    foreach (var item in result)

                    {

                        str.Append(item + ",  ");

                    }

                    res.info ="导入EXCEL中包含重复ISBN'  "+ str.ToString()+"'  请整理后再重新导入";

                    return res;

                }