查询结果不能枚举多次错误答案

【问题标题】：query results cannot be enumerated more than once error查询结果不能枚举多次错误
【发布时间】：2010-02-11 16:17:52
【问题描述】：

我有一个问题，我两次调用一个存储的过程，每个都有不同的参数，我需要 2 个单独的列表，但 linq 正在缓存数据并给我上面的错误

我尝试了 2 种不同的方法来绕过错误消息，一种在 tbl 上使用 ToList()，另一种手动遍历数据

我的代码如下所示

获取总数的代码

  public static List<MeterTotalConsumpRecord> GetTotalAllTimesConsumption(DateTime dtStart, DateTime dtEnd, EUtilityGroup ug, int nMeterSelectionType, int nCustomerID, 
        int nUserID, string strSelection, bool bClosedLocations, bool bDisposedLocations)
    {

        dbChildDataContext db = DBManager.ChildDataConext(nCustomerID);

        db.MeterTotalConsumpRecordSet.MergeOption = System.Data.Objects.MergeOption.NoTracking;
        var tbl = from t in db.GetTotalConsumptionByMeter(dtStart, dtEnd, (int) ug, nMeterSelectionType, nCustomerID, nUserID, strSelection, bClosedLocations, bDisposedLocations, 1)                       
                  select t;

        List<MeterTotalConsumpRecord> objList = new List<MeterTotalConsumpRecord>();

        foreach (MeterTotalConsumpRecord objRecord in tbl)
        {
            objList.Add(objRecord);
        }
        return objList;

    }

    public static List<MeterTotalConsumpRecord> GetTotalDayConsumption(DateTime dtStart, DateTime dtEnd, EUtilityGroup ug, int nMeterSelectionType, int nCustomerID,
                int nUserID, string strSelection, bool bClosedLocations, bool bDisposedLocations)
    {
        dbChildDataContext db = DBManager.ChildDataConext(nCustomerID);
        db.MeterTotalConsumpRecordSet.MergeOption = System.Data.Objects.MergeOption.NoTracking;
        var tbl = from t in db.GetTotalConsumptionByMeter(dtStart, dtEnd, (int)ug, nMeterSelectionType, nCustomerID, nUserID, strSelection, bClosedLocations, bDisposedLocations, 3)
                  select t;

        return tbl.ToList();
    }

{

...Code for setting properties using parameters..

_P2Totals = ProfileDataService.DataService.GetTotalAllTimesConsumption(_P2StartDate, _P2EndDate, EUtilityGroup.Electricity, 1, nCustomerID, nUserID, strLocations, bIncludeClosedLocations, bIncludeDisposedLocations);

    _P1Totals = ProfileDataService.DataService.GetTotalAllTimesConsumption(_StartDate, _EndDate, EUtilityGroup.Electricity, 1, nCustomerID, nUserID, strLocations, 
        bIncludeClosedLocations, bIncludeDisposedLocations);


    PopulateLines() //This fills up a list of objects with information for my report ready for the totals to be added

    PopulateTotals(_P1Totals, 1);
    PopulateTotals(_P2Totals, 2);

}

第二次进入 GetTotalAllTimesConsumption 时出现错误

有没有办法可以回到列表的开头？有一个名为 FirstOrDefault 的方法不确定这是否有帮助？

干杯

保罗

【问题讨论】：

请格式化您的代码。

标签： linq linq-to-sql linq-to-objects

【解决方案1】：

您遇到了什么错误？你没有指定它。尝试在每次调用时重新创建数据上下文？

Ps：要在 linq 查询上转换为列表，您只需在 linq 查询的结果上调用 .ToList()

【讨论】：