c# - 如何避免MySql/net连接器中的 "There is already an open DataReader associated with this Connection which must be closed first."？

我有以下这段代码:

public TimestampedRowStorage GetTimestampedRowStorage(string startTime, string endTime, long trendSettingID, int? period)
    {
        var timestampedList = (from t in dataContext.TrendRecords
                                     where t.TrendSetting_ID == trendSettingID
                                     select t).ToList();

        return new TimestampedRowStorage
        {
            TimestampedDictionary = timestampedList.ToDictionary(m => m.Timestamp,
                m => (from j in dataContext.TrendSignalRecords
                      where j.TrendRecord_ID == m.ID
                      select j).ToDictionary(p => p.TrendSignalSetting.Name,
                p => (double?)p.Value))
        };
    }

但是我总是得到以下异常:



这是堆栈跟踪:



你们能帮我吗？

最佳答案

该错误可能是因为您在访问数据库时尝试访问数据库。
您应该尝试将两个Linq表达式分开。
也许这样写:

var TimestampedList = (from t in dataContext.TrendRecords
                                         where t.TrendSetting_ID == trendSettingID
                                         select t).ToList();
TimestampedDictionary = timestampedList.ToDictionary(m => m.Timestamp,
                    m => (from j in dataContext.TrendSignalRecords
                          where j.TrendRecord_ID == m.ID
                          select j).ToDictionary(p => p.TrendSignalSetting.Name,
                    p => (double?)p.Value))

关于c# - 如何避免MySql/net连接器中的 "There is already an open DataReader associated with this Connection which must be closed first."？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/6271971/