IEnumerable踩过的坑

1.

查询接口：建议使用IEnumerable

更新、创建接口：不要使用IEnumerable（maybe 接口会重复调用）；建议使用可以讲结果保存到内存中的类型（like：IList、IDictionary）

                
                var result = _serviceItemConsumeRecordSvc.Add(consumeResult).ToList();
//if _serviceItemConsumeRecordSvc.Add return as IEnumerable<object>
//warn,first call Add():result.Any()
                if (result == null || !result.Any())
                {
                    var msg = $"no serviceItemConsumeRecord can be added";
                    _loger.Warn(msg,  consumeResult );
                    yield return new SPOSpendingActionResponseItem()
                    {
                        Sucess = false,
                        Message = msg
                    };
                    continue;
                }
                #endregion

                #region return
//warn,second call Add(): foreach (var itemResult in result)
                foreach (var itemResult in result)
                {
                   //……
                }
                #endregion            

　　

2.

foreach 循环中 yield return 之后，记得添加：continue

非 foreach 循环中 ：返回 yield break;（yield return null之后，后续代码仍旧会执行）

        public IEnumerable<SPOUsedSearchExtendResponseItem> UsedRecordFullSearch(SPOUsedSearchExtendRequest req)
        {
            var usedRecords = UsedRecordsSearch(req);
            if (usedRecords == null || usedRecords.Data == null || !usedRecords.Data.Any())
            {
//warn ：use "yield break" instead of "yield return null"(;
//otherwise [ var consumerRecordLK = usedRecords.Data.ToLookup(_ => _.ProduceRecordNumber);] will execute
                yield break;
            }
            var consumerRecordLK = usedRecords.Data.ToLookup(_ => _.ProduceRecordNumber);
            //……
        }
    

　　

                #region return
                foreach (var itemResult in result)
                {
                    if (!itemResult.IfSuccess || itemResult.SICRs == null || !itemResult.SICRs.Any())
                    {

                        yield return new SPOSpendingActionResponseItem()
                        {
                            Sucess = itemResult.IfSuccess,
                            SICR = itemResult.SICRs!=null? itemResult.SICRs.ToList():null,
                            Message = itemResult.Message
                        };
// warn：
// if： in foreach， yield return & not end continue
// then：【 var produceRecordNumbers = itemResult.SICRs.Select(_ => _.ProduceRecordNumber); 】will execute，instead of skip to foreach 
                        continue;
                    }
                    var produceRecordNumbers = itemResult.SICRs.Select(_ => _.ProduceRecordNumber); 
                   //……
                }
                #endregion