我创建了以下DTO：

    public class TestAndQuestionDTO
    {
        public string Name { get; set; }
        public int QuestionsCount { get; set; }
        public ICollection<TestAndQuestionDTO.Questions> TestQuestions { get; set; }

        public class Questions
        {
            public Guid QuestionUId { get; set; }
        }
    }

我试图用LINQ来填充它,但是我仍然坚持如何填充内部的Questions类.

这是我到目前为止的内容：

    var result = await db.Tests
            .Include(t => t.TestQuestions)
            .Where(t => t.TestId == id)
            .Select(t => new TestAndQuestionDTO
            {
                Name = t.Title,
                TestQuestions = new TestAndQuestionDTO.Questions
                {
                    QuestionUId = t.TestQuestions. ????
                }

            })
            .ToListAsync();

有人可以告诉我如何使用从我的集合中带回来的数据填充TestQuestions集合字段：.Include(t => t.TestQuestions)我是否必须例如在TestAndQuestionDTO中有一个构造函数来创建一个集合的TestQuestions？

这是我的Test类供参考：

public partial class Test
{
    public Test()
    {
        this.TestQuestions = new HashSet<TestQuestion>();
    }

    public int TestId { get; set; }
    public string Title { get; set; }
    public virtual ICollection<TestQuestion> TestQuestions { get; set; }

}

解决方法:

您可以使用另一个“选择”将其转换为“问题” DTO,如下所示：

var result = await db.Tests
        .Include(t => t.TestQuestions)
        .Where(t => t.TestId == id)
        .Select(t => new TestAndQuestionDTO
        {
            Name = t.Title,
            TestQuestions = t.TestQuestions.Select(tq => new TestAndQuestionDTO.Questions
            {
                QuestionUId = tq.QuestionUId,
                //fill in your Questions DTO here
            })

        })
        .ToListAsync();

如果您需要TestAndQuestionDTO.Questions成为ICollection<>类型,将其更改为此：

var result = await db.Tests
        .Include(t => t.TestQuestions)
        .Where(t => t.TestId == id)
        .Select(t => new TestAndQuestionDTO
        {
            Name = t.Title,
            TestQuestions = new Collection<TestAndQuestionDTO.Questions>(
                t.TestQuestions.Select(tq => new TestAndQuestionDTO.Questions
                {
                    QuestionUId = tq.QuestionUId,
                    //fill in your Questions DTO here
                }).ToList())
        })
        .ToListAsync();