Question

我有两个表News和Comments。 Comments表具有两个外键列UserId和NewsId。

当我在Entity Framework Core中通过ID获得News项时，注释为空。

新闻模型类：

public partial class News
{
    public News()
    {
        NewsComments = new HashSet<NewsComments>();
        NewsLikes = new HashSet<NewsLikes>();
    }

    public int Id { get; set; }
    public string Title { get; set; }
    public string Text { get; set; }
    public string Thumbnail { get; set; }
    public string Image { get; set; }
    public DateTime? Date { get; set; }
    public int CategoryId { get; set; }
    public int PublisherId { get; set; }
    public int? ViewCount { get; set; }
    public int? LikeCount { get; set; }
    public int? CommentCount { get; set; }

    public virtual NewsCategories Category { get; set; }
    public virtual NewsPublishers Publisher { get; set; }
    public virtual ICollection<NewsComments> NewsComments { get; set; }
    public virtual ICollection<NewsLikes> NewsLikes { get; set; }
}

评论模型类：

public partial class NewsComments
{
    public int Id { get; set; }
    public int UserId { get; set; }
    public int NewsId { get; set; }
    public string Text { get; set; }
    public DateTime? Date { get; set; }
    public bool? IsAccept { get; set; }

    public virtual News News { get; set; }
    public virtual Users User { get; set; }
}

获取新闻方法：

public News GetNews(int id)
{
    return _db.News.Find(id);
}

Answer 1

在EF中，如果默认设置是急切加载，则需要像这样包含关系的model属性：

public News GetNews(int id)
{
    return _db.News.Include(n=>n.NewsComments).Find(id);
}

除非您被迫延迟加载，但仍然必须在上下文中设置关系

modelBuilder.Entity<NewsComments>(entity =>
{
    entity.HasOne(nc => nc.News)
    .WithMany(n => n.NewsComments)
    .HasForeignKey(nc => nd.NewsId);
 });

实体框架核心中的一对多关系

1 个答案: