EF Core 在使用 Include 时避免加载父实体

Question

I have the following code

public class Question
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long Id { get; set; }

    [Required]
    public string QuestionText { get; set; }

    public virtual ICollection<QuestionOption> QuestionOptions { get; set; }
}

public class QuestionOption
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long Id { get; set; }

    [Required]
    public string OptionText { get; set; }

    [ForeignKey("QuestionId")]
    public Question Question { get; set; }
    public long QuestionId { get; set; }

    public virtual ICollection<QuestionOptionAnswer> QuestionOptionAnswers { get; set; }
}

public class QuestionOptionAnswer
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long Id { get; set; }

    [ForeignKey("QuestionOptionId")]
    public QuestionOption QuestionOption { get; set; }
    public long QuestionOptionId { get; set; }
}

and the following query to retrieve the question:

var dbResult = await (from question in context.Question.Include(x => x.QuestionOptions).ThenInclude(x => x.QuestionOptionAnswers)
                                  where question.Id == id
                                  select question).FirstOrDefaultAsync();

Everything works fine and the query returns what I really need except from the fact that I can see in a QuestionOption the parent Entity(Question) which I already have. I have cases that I have 10 question options for a question and each one has the Question parent entity returned. This is not desired as I am getting the same thing I already have multiple times. How can I prevent this from happening?

Answer 1

You aren't getting the parent object multiple times, each parent is returned as a single row from the database and one object is created for each Question .

It is referenced in multiple places though, including in your QuestionOption , which as little impact on performance.