c# - Linq 过滤嵌套列表

Question

好的，我在下面写了 LINQ to Entities 查询(足够接近下面显示的我的 c# 查询)

var itemss = filteredstudents
.Where(x => x.SubjectTypes.Any(y => y.SubjectItem.Any(z => z.Name  == value1))).ToList();

仍然没有什么问题，因为当 SubjectItem 类型有两个元素并且其中一个与 value1 匹配时。它仍然返回两者。它应该只返回匹配的记录。我知道问题出在 Any 上，但不确定 Any 应该替换成什么？

foreach (StudentDTO student in filteredstudents)
{
    bool valid = true;
    foreach (SubjectTypes subjectType in student.SubjectTypes)
    {
        string value1 = subjectType.SubjectItem.Select(x => x.value1).First();
        Guid StId = _context.Items.Where(x => x.Name == value1).FirstOrDefault();

        if (StId != null)
            valid = true;
        else
        {
            valid = false;
            _log("create log");
        }
    }
    if (valid)
        filteredstudentsWithUnits.Add(student);
}

示例输入

{"Name":"ABC",
"Age":12,
,"SubjectTypes":
[
{"Id":"1","Description":""Description","SubjectItem":[{"Id":"1","Marks":12,"Name":"aaa"}]},
{"Id":"1","Description":""Description","SubjectItem":[{"Id":"1","Marks":12,"Name":"aaa"}]},
{"Id":"1","Description":""Description","SubjectItem":[{"Id":"1","Marks":12,"Name":"bbb"}]}
]
}

预期输出

{"Name":"ABC",
"Age":12,
,"SubjectTypes":
[
{"Id":"1","Description":""Description","SubjectItem":[{"Id":"1","Marks":12,"Name":"aaa"}]},
{"Id":"1","Description":""Description","SubjectItem":[{"Id":"1","Marks":12,"Name":"aaa"}]},

]
}

Answer 1

您可以先使用 .Where 过滤列表，然后使用 .Select 投影到仅包含所需数据的新集合。像下面这样的东西可能会起作用:

var itemss = filteredstudents
    .Where(s => s.SubjectTypes.Any(st => st.SubjectItem.Any(si => si.Name  == value1)))
    .Select(s => new StudentDTO
    {
        Name = s.Name,
        Age = s.Age,
        SubjectTypes = s.SubjectTypes.Where(st => st.SubjectItem.Any(si => si.Name  == value1))
            .Select(st => new SubjectType
            {
                Id = st.Id,
                Description = st.Description,
                SubjectItem = st.SubjectItem.Where(si => si.Name == value1).ToList()
            }).ToList()
    })
    .ToList();