Search order by externalId error

@operator

I am a novice,and My English is not very good.I want to search order by externalId ,but i am  fail search,can you tell me How to solve it.     

TransactionSearch transactionSearch = new TransactionSearch();
            TransactionSearchBasic transactionSearchBasic = new                    TransactionSearchBasic();
            RecordRef[] arryrec = new RecordRef[2];
            RecordRef subsl = new RecordRef();
            subsl.type = RecordType.subsidiary;
            subsl.internalId = "15";
            arryrec[0] = subsl;
            RecordRef exid = new RecordRef();
            exid.type = RecordType.salesOrder;
            exid.externalId = TextBox1.Text.Trim();
            exid.typeSpecified = true;
            arryrec[1] = exid;
            SearchMultiSelectField externalId = new SearchMultiSelectField();
            externalId.@operator = SearchMultiSelectFieldOperator.noneOf;
            externalId.operatorSpecified = true;
            externalId.searchValue = arryrec;
            transactionSearchBasic.externalId = externalId;
            transactionSearch.basic = transactionSearchBasic;
           
            SearchResult searchRes = _service.search(transactionSearch);