EF包含填充ViewModel

Question

在Entity Framework的帮助下检索数据时，我想填充子ViewModel，它恰好是一个集合。下面的查询工作正常，但只使用子模型（集合）的第一项填充内部ViewModel。如何使用所有相应的模型数据填充内部ViewModel。

var pagedQuestions = _ctx.VoteQuestions.Include(q => q.VoteAnswerOptions).Select(q => new Question
{
    QuestionStr = q.Name,
    QuestionId = q.Id,
    IsMultipleAnswerQuestion = q.VoteType.Id == 1 ? false : true,
    PossibleAnswers = new List<PossibleAnswer>
    {
        new PossibleAnswer
        {
            AnswerId = q.VoteAnswerOptions.FirstOrDefault().Id,
            AnswerStr = q.VoteAnswerOptions.FirstOrDefault().Answer
        }
    }
});

Answer 1

您可以在第一个Select内完成第二个Select：

var pagedQuestions = _ctx.VoteQuestions.Select(q => new Question
{
    QuestionStr = q.Name,
    QuestionId = q.Id,
    IsMultipleAnswerQuestion = q.VoteType.Id == 1 ? false : true,
    PossibleAnswers = q.VoteAnswerOptions
                       .Select(a => new PossibleAnswer
                                {
                                    AnswerId = a.Id,
                                    AnswerStr = a.Answer
                                }
                              )
    }
});

您不需要Include。实体框架将加入VoteAnswerOptions本身，并从中选择所需的字段。