我很难调试一些 LINQ to SQL 代码，因为没有调用堆栈，而且我不知道错误发生在哪里。这似乎不是 SQL 错误 - 它在 C# 中，但通过搜索和其他所有内容，我找不到任何方法来确定哪个计算给出了错误。
源代码如下，您可以看到当我尝试插入一些新行时抛出的错误。调用堆栈为空，并且异常不包含有关问题所在的信息。
var groups =
from record in startTimes
group record by record.startTime
into g
select new
{
startTime = g.Key.GetValueOrDefault(),
totalTasks = g.Count(),
totalTime = g.Max(o => o.record.timeInSession).GetValueOrDefault(),
minDwell = g.Min(o => o.record.dwellTime).GetValueOrDefault(),
maxDwell = g.Max(o => o.record.dwellTime).GetValueOrDefault(),
avgDwell = g.Average(o => o.record.dwellTime).GetValueOrDefault(),
stdevDwell = g.Select(o => Convert.ToDouble(o.record.dwellTime)).StdDev(),
correct80 = g.Sum( o => o.record.correct80.GetValueOrDefault() ? 1 : 0),
wrong80 = g.Sum(o => o.record.wrong80.GetValueOrDefault() ? 1 : 0)
};
var statistics = groups.AsEnumerable().Select(
g => new e_activeSession()
{
workerId = wcopy,
startTime = g.startTime,
totalTasks = g.totalTasks,
totalTime = g.totalTime,
minDwell = g.minDwell,
maxDwell = g.maxDwell,
avgDwell = g.avgDwell,
stdevDwell = g.stdevDwell,
total80 = g.correct80 + g.wrong80,
correct80 = g.correct80,
percent80 = g.correct80 / (g.correct80 + g.wrong80)
}
);
// Put these rows into the table
_gzClasses.e_activeSessions.InsertAllOnSubmit(statistics);
_gzClasses.SubmitChanges();
这是异常的堆栈跟踪。如果有人能破译它，请告诉我，因为我不知道如何阅读这些匿名类型......
at System.Data.SqlClient.SqlBuffer.get_Double()
at System.Data.SqlClient.SqlDataReader.GetDouble(Int32 i)
at Read_<>f__AnonymousType2`9(ObjectMaterializer`1 )
at System.Data.Linq.SqlClient.ObjectReaderCompiler.ObjectReader`2.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at System.Data.Linq.Table`1.InsertAllOnSubmit[TSubEntity](IEnumerable`1 entities)
另外，我在 LINQPad 中运行了这个查询并得到了相同的错误和堆栈跟踪。最后，这是 LINQ to SQL 生成的数据库查询，该查询在错误发生前执行。我根本看不到任何双重转换。
SELECT COALESCE([t5].[value22],'1/1/0001 12:00:00 AM') AS [startTime], [t5].[value] AS [totalTasks], COALESCE([t5].[value2],0) AS [totalTime], COALESCE([t5].[value3],0) AS [minDwell], COALESCE([t5].[value4],0) AS [maxDwell], COALESCE([t5].[value5],0) AS [avgDwell], [t5].[value6] AS [correct80], [t5].[value7] AS [wrong80], [t5].[value22]
FROM (
SELECT COUNT(*) AS [value], MAX([t4].[timeInSession]) AS [value2], MIN([t4].[dwellTime]) AS [value3], MAX([t4].[dwellTime]) AS [value4], AVG([t4].[dwellTime]) AS [value5], SUM([t4].[value3]) AS [value6], SUM([t4].[value]) AS [value7], [t4].[value2] AS [value22]
FROM (
SELECT
(CASE
WHEN (COALESCE([t3].[wrong80],0)) = 1 THEN @p4
ELSE @p5
END) AS [value], [t3].[workerID], [t3].[value2], [t3].[timeInSession], [t3].[dwellTime], [t3].[value] AS [value3]
FROM (
SELECT
(CASE
WHEN (COALESCE([t2].[correct80],0)) = 1 THEN @p2
ELSE @p3
END) AS [value], [t2].[wrong80], [t2].[workerID], [t2].[value] AS [value2], [t2].[timeInSession], [t2].[dwellTime]
FROM (
SELECT (
SELECT MAX([t1].[timeStamp])
FROM [dbo].[workerLog] AS [t1]
WHERE ([t1].[dwellTime] IS NULL) AND ([t1].[timeInSession] = @p0) AND ([t1].[workerID] = @p1) AND ([t1].[timeStamp] <= [t0].[timeStamp])
) AS [value], [t0].[workerID], [t0].[dwellTime], [t0].[timeInSession], [t0].[correct80], [t0].[wrong80]
FROM [dbo].[workerLog] AS [t0]
) AS [t2]
) AS [t3]
) AS [t4]
WHERE [t4].[workerID] = @p6
GROUP BY [t4].[value2]
) AS [t5]