LINQ查询求助：产品测试结果的三类状态统计及二次查询问题

我有一张产品测试结果表MfgTests，测试可能因多种原因失败，需要统计以下三类数据：

• 整体通过的测试总数
• 门开关测试失败且从未通过的测试数
• 门开关首次测试失败但后续通过的测试数

每条记录包含唯一UID和日期时间字段，同一产品可被多次测试。目前我写的LINQ代码能正确统计前两类数据，但第三类数据的统计存在问题：在测试数据中预期结果应为1（对应UID 10），但现有代码返回4；调整后的代码在测试数据中能得到正确结果，但在真实数据里无效。

现有代码：

var totalPass = (from d in KAKs
                where d.TestResult == "PASS"
                select d);
Console.WriteLine("Total Passing: \t" + totalPass.Count());

var dataPass = (from d in KAKs
                where d.DoorSwitch == "PASS"
                select d);
Console.WriteLine("Total Door Switch Passes: \t" + dataPass.Count());
var dataFail = (from d in KAKs
                where d.DoorSwitch == "FAIL"
                select d);
Console.WriteLine("Total Door Switch Fails: \t" + dataFail.Count());

foreach (var uid in dataFail)
{
    Console.WriteLine(uid.UID);
    var distinctPass =
        from list in dataPass
        group list by list.UID into grouped
        where grouped.Count() == 1
        select grouped;
    Console.WriteLine("Door Switch Fail but pass later: \t" + distinctPass.Count());
}

调整后的代码：

var distinctPass =
    from list in dataPass
    group list by list.UID into grouped
    where grouped.Count() != 1
    select grouped;
Console.WriteLine("Door Switch Fail but pass later: \t" + distinctPass.Count());

内容的提问来源于stack exchange，提问作者EE_Kraig