我可以在LINQ查询中的孙子项上使用where子句吗? [英] Can I have a where clause that works on a grandchild in a LINQ query?

问题描述

我有三个表，每个表都与一个主键和外键(如TestId和UserTestId等)连接.

I have three tables that are each connected with a primary key and foreign key such as TestId and UserTestId etc.

Exam > Test > UserTest

据我了解，我可以使用LINQ从这些数据中获取数据，如下所示:

It's my understanding I can use LINQ to get the data from these like this:

        var exams = _examsRepository
       .GetAll()
       .Where(q => q.SubjectId == subjectId)
       .Include(q => q.Tests.Select(t => t.UserTests))
       .ToList();

这将选择所有考试，针对考试的考试和针对其中SubjectId == subjectID的那些考试的UserTest

This will select all the exams, Tests for the exams and UserTests for those Tests where SubjectId == subjectID

有什么办法可以进一步限制它，使其仅在UserTests的UserId为123时显示数据?

Is there any possible way I could further limit this so that it only showed the data for when the UserTests had a UserId of 123?

如果答案是否定的，那么我应该重写此LINQ，以便首先转到_userTestsRepository，然后朝另一个方向(而不是向下)工作吗?

If the answer is no then should I rewrite this LINQ to first go to the _userTestsRepository and then work in the other direction up instead of down?

推荐答案

在此问题中他们提供了可以满足您需求的解决方案，但我认为这有点像hack.
或者，您可以退出include语句并进行手动联接，可以按照需要在子表上应用尽可能多的过滤器.
可能看起来像这样:

In this question they offer a solution which does what you want but in my opinion feels a little like a hack.
Alternatively you could step away from include statements and do a manual join, you can apply as many filters on sub tables as you like that way.
Could look a lil like this :

var data = (from ex in context.exams
           join t in context.tests on ex.Id equals test.ExamID
           join ut in context.userTests on t.Id equals ut.TestId
           where ut.UserId = 123
           select new {ex, ut}).ToList();

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