LINq d 多个datatable 连接查询

就是把两个datatable 用CompanyName 连接一下。 为啥本人的 query 一直是没值的。求高手解救。

           
 var query = from t1 in dt.AsEnumerable()
                        join t2 in ds.Tables[0].AsEnumerable()
                        on t1.Field<string>("CompanyName") equals t2.Field<string >("CompanyName") 
                        select new
                        {
                            CompanyCode = t2.Field<string>("Companycode"),
                            JournalType=t1.Field<string>("JournalType"),
                            AccountType=t1.Field<string>("AccountType"),
                            Acckind =t1.Field<string>("Acckind"),
                        };
        
            //var noList = JsonConvert.DeserializeObject<List<string>>(selectvalue);
            foreach (var obj in query)
                {
                  dtall.Rows.Add(obj.CompanyCode, obj.JournalType, obj.AccountType, obj.Acckind);
                }