C# 林克。要求了解C语言中的多个“选择与从”和“位置”

我是LINQ的新手，在阅读一些代码时遇到了麻烦。我不想找人向我解释代码，而是想知道：

首先，我需要了解哪些合适的搜索词。例如，当您有多个Select语句时，您将其称为什么。我的直觉是这是一个内部连接，但我不熟悉LINQ语法

第二，能给我指一些参考资料吗？我已经试过了，但我认为我无法找到合适的搜索词限制了我。我要么提出简单的fromselect语句，要么提出内部连接语句

代码：

---

这个查询非常难看，所以我为您分析了它。希望您能够更轻松地解析：

// Find the nations whose name matches nationReportAbbr
// Find the nations whose name matches nationReportAbbr
var matchingNations = _database.SessionDatabaseObject.Nations.Where(nation =>
    String.Equals(nation.ReportAbbreviation, nationReportAbbr, StringComparison.CurrentCultureIgnoreCase));
if (matchingNations.Any())
{
    Nation matchingNation = matchingNations.First();

    // Find the sexes whose name matches sexReportAbbr
    var matchingSexes = _database.SessionDatabaseObject.Sexes.Where(sex =>
        String.Equals(sex.Name, sexReportAbbr, StringComparison.CurrentCultureIgnoreCase));
    if (matchingSexes.Any())
    {
        Sex matchingSex = matchingSexes.First();

        // Find the recording sites with the appropriate nation and sex
        var matchingRecordingSites = _database.SessionDatabaseObject.RecordingSites.Where(recordingSite =>
            recordingSite.NationId == matchingNation.Id && recordingSite.SexId == matchingSex.Id);
        if (matchingRecordingSites.Any())
        {
            RecordingSite matchingRecordingSite = matchingRecordingSites.First();

            // Find the interviewers with the appropriate recording site
            var matchingInterviewers = _database.SessionDatabaseObject.Interviewers.Where(interviewer =>
                interviewer.RecordingSiteId == matchingRecordingSite.Id);
            if (matchingInterviewers.Any())
            {
                Interviewer matchingInterviewer = matchingInterviewers.First();

                // Find the readings taken by the appropriate interviewer whose RunEventId matches the provided _entry.Id
                var matchingReadings = _database.SessionDatabaseObject.Readings.Where(reading =>
                    reading.InterviewerId == matchingInterviewer.Id
                    && reading.RunEventId == _entry.Id);
                if (matchingReadings.Any())
                {
                    Reading matchingReading = matchingReadings.First();

                    // Find the height
                    float? height = matchingReading.Height;
                    if (height.HasValue)
                    {
                        return ((int)Math.Floor(height.Value)).ToString();
                    }
                }
            }
        }
    }
}

return String.Empty;

---

这个查询非常难看，所以我为您分析了它。希望您能够更轻松地解析：

// Find the nations whose name matches nationReportAbbr
// Find the nations whose name matches nationReportAbbr
var matchingNations = _database.SessionDatabaseObject.Nations.Where(nation =>
    String.Equals(nation.ReportAbbreviation, nationReportAbbr, StringComparison.CurrentCultureIgnoreCase));
if (matchingNations.Any())
{
    Nation matchingNation = matchingNations.First();

    // Find the sexes whose name matches sexReportAbbr
    var matchingSexes = _database.SessionDatabaseObject.Sexes.Where(sex =>
        String.Equals(sex.Name, sexReportAbbr, StringComparison.CurrentCultureIgnoreCase));
    if (matchingSexes.Any())
    {
        Sex matchingSex = matchingSexes.First();

        // Find the recording sites with the appropriate nation and sex
        var matchingRecordingSites = _database.SessionDatabaseObject.RecordingSites.Where(recordingSite =>
            recordingSite.NationId == matchingNation.Id && recordingSite.SexId == matchingSex.Id);
        if (matchingRecordingSites.Any())
        {
            RecordingSite matchingRecordingSite = matchingRecordingSites.First();

            // Find the interviewers with the appropriate recording site
            var matchingInterviewers = _database.SessionDatabaseObject.Interviewers.Where(interviewer =>
                interviewer.RecordingSiteId == matchingRecordingSite.Id);
            if (matchingInterviewers.Any())
            {
                Interviewer matchingInterviewer = matchingInterviewers.First();

                // Find the readings taken by the appropriate interviewer whose RunEventId matches the provided _entry.Id
                var matchingReadings = _database.SessionDatabaseObject.Readings.Where(reading =>
                    reading.InterviewerId == matchingInterviewer.Id
                    && reading.RunEventId == _entry.Id);
                if (matchingReadings.Any())
                {
                    Reading matchingReading = matchingReadings.First();

                    // Find the height
                    float? height = matchingReading.Height;
                    if (height.HasValue)
                    {
                        return ((int)Math.Floor(height.Value)).ToString();
                    }
                }
            }
        }
    }
}

return String.Empty;

---

这些是嵌套查询。您可以在这里找到信息：这对您来说应该是一个好的开始，查询似乎是由不知道Linq连接的人完成的。我喜欢所有这些第一次调用。派对上的乐趣。@Ryk-你讨厌Linq，因为有人会写一行糟糕的Linq行？相信我，他的查询看起来也一样难看。这些是嵌套查询。您可以在这里找到信息：这对您来说应该是一个好的开始，查询似乎是由不知道Linq连接的人完成的。我喜欢所有这些第一次调用。派对上的乐趣。@Ryk-你讨厌Linq，因为有人会写一行糟糕的Linq行？相信我，他的问题看起来也一样难看。