LINQ 查詢以獲取有關 object 的所有數據，這是當集合的每個項目都有自己的集合時的對象集合

Question

誰能給我一個關於如何解決下一個任務的提示？

我有這樣的類結構

public class Test
{
    public string Title { get; set; }
    public ICollection<Question> Questions { get; set; }
}

public class Question
{
    public string Description { get; set; }
    public ICollection<AnswerItem> AnswerItems { get; set; }
}

public class AnswerItem
{
    public string Defenition { get; set; }
    public bool IsCorrect { get; set; }
}
   

從數據庫中獲取[Test]實體后，我得到了IQueryable<Test> 。 此外，我想知道如何獲取所有問題實體（作為列表）以及所有信息，其中每個問題項都將包含有關 AnswerItem 集合的所有信息。 我嘗試了下一個查詢，但它只返回所有答案的集合：

var questList = test.SelectMany(t => t.Questions.SelectMany(q => q.AnswerItems)).ToList();

我需要這樣的東西：

Questions = new List<Question>
{
    new Question
    {
        Name = "Question_1",
        AnswerItems = new List<AnswerItem>
        {
            new AnswerItem { Name = "answer_1", IsCorrect = false },
            new AnswerItem { Name = "answer_2", IsCorrect = false }
        }
    },
    new Question
    {
        Name = "Question_2",
        AnswerItems = new List<AnswerItem>
        {
            new AnswerItem { Name = "answer_1", IsCorrect = false },
            new AnswerItem { Name = "answer_2", IsCorrect = false }
        }
    }
}

Answer 1

您的查詢應如下所示：

var query =
    from t in ctx.Tests
    from q in t.Questions
    select new
    {
        Name = q.Description,
        AnswerItems = q.AnswerItems.Select(a => new 
            { 
                Name = a.Defenition, 
                IsCorrect = a.IsCorrect
            })
            .ToList()
        }
    };

var result = query.ToList();