无法使用 Include 或 ThenInclude 或 Select/Many with ONE 查询加载相关数据 [英] Can not load related data with Include or ThenInclude or Select/Many with ONE query

问题描述

1 个测试分配了 1 个测试类型.

1 Test has 1 TestType assigned.

我需要加载与 Test 相关的所有 TestType 实体或 not 和 Schoolclass 、Subject 和指定的学生到测试 (PupilsTests)

I need to load all TestType entities with relation to a Test OR not and Schoolclass , Subject and Assigned Pupils to a test (PupilsTests)

.SelectMany 或 .Select 在运行时在这里失败.

The .SelectMany or .Select fails here during runtime.

我尝试了 Include 和 ThenInclude 的不同组合，但没有机会通过 PupilsTests 获得测试.

I tried different combinations of Include and ThenInclude but no chance to get the Tests WITH the PupilsTests.

当我使用 context.Tests

但这导致我只得到分配给测试的测试类型- innerjoin - 但我需要所有的测试类型和他们的测试和他们的学生测试，我希望它在一个查询中.

but that has the consequence that I get only the TestTypes assigned to a Test - innerjoin - but I need all TestTypes and their Tests and their PupilsTests and I want it in ONE query.

var testtypes = await context.TestTypes
                   .Include(x => x.Schoolclass)
                   .Include(x => x.Subject)
                   .Include(x => x.Tests.SelectMany(z => z.PupilsTests))
              .Where(t => t.SchoolyearId == schoolyearId)
              .AsNotTracking()
              .ToListAsync();



        public class TestType
{
    public TestType()
    {
        Tests = new HashSet<Test>();
    }
    // Props removed for clarity
    public int Id { get; set; }   
    public ISet<Test> Tests { get; set; }
    public Schoolyear Schoolyear { get; set; }  
    public Schoolclass Schoolclass { get; set; }   
    public Subject Subject { get; set; }
    public int SchoolyearId { get; set; }
}

  public class Test
    {
        public Test()
        {
            PupilsTests = new HashSet<PupilTest>();
        }
        // Props removed for clarity
        public int Id { get; set; }           
        public ISet<PupilTest> PupilsTests { get; set; }
        public TestType TestType { get; set; }


    }

推荐答案

EF Core 等效于 EF6 的语法

The EF Core equivalent syntax of EF6

.Include(x => x.Tests.SelectMany(z => z.PupilsTests))

是

.Include(x => x.Tests).ThenInclude(x => x.PupilsTests)

请注意，ThenInclude 中似乎存在 VS Intellisense 问题，因此只需键入以上内容，它就会成功编译并运行.

Note that there seems to be a VS Intellisense issue inside the ThenInclude, so just type the above and it will compile successfully and work.

另请注意，EF Core 处理集合包含的内容不同(不像在 EF6 中那样使用单个查询)，因此上面会生成并执行 3 个 SQL 查询.

Also please note that EF Core processes collection includes differently (does not use single query as in EF6), so the above would generate and execute 3 SQL queries.

更新: VS Intellisense 问题现在在 包括多个级别部分:

Update: The VS Intellisense issue now is specifically mentioned in the EF Core documentation under Including multiple levels section:

注意！

当前版本的 Visual Studio 提供不正确的代码完成选项，并且在集合导航属性之后使用 ThenInclude 方法时，可能会导致正确的表达式被标记为语法错误.这是在 https://github.com/dotnet/roslyn/上跟踪的 IntelliSense 错误的症状问题/8237.只要代码正确并且可以成功编译，就可以安全地忽略这些虚假的语法错误.

Current versions of Visual Studio offer incorrect code completion options and can cause correct expressions to be flagged with syntax errors when using the ThenInclude method after a collection navigation property. This is a symptom of an IntelliSense bug tracked at https://github.com/dotnet/roslyn/issues/8237. It is safe to ignore these spurious syntax errors as long as the code is correct and can be compiled successfully.

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