Question

我有新闻。一个新闻可以有许多标签，类别和图像。关于扩展模型我很特别。

public class NewsExt
    {
        public News News { get; set; }
        public List<Categories> Categories { get; set; }
        public List<Images> Images { get; set; }
        public List<Tags> Tags { get; set; }
    }

或

public class NewsExt
    {
        public Base.News News { get; set; }
        public Categories Categories { get; set; }
        public Images Images { get; set; }
        public Tags Tags { get; set; }
    }

我使用第二种变体并想要这样的东西：

    return
    ((from n in db.News
      from i in db.Images.DefaultIfEmpty()
      from t in db.Tags.DefaultIfEmpty()
      from c in db.Categories.DefaultIfEmpty()
      select new NewsExt()
      {
          News = n,
          Images = i,
          Tags = t,
          Categories = c
      }).GroupBy(news => news.News))

我希望* NewsExt数组**包含一个新闻和所有其他实体，而不重复此数组的每个元素。对于第一个视图模型，我尝试：

(from n in db.News
          select new NewsExt()
          {
              News = n,
              Images = (from i in db.Images.DefaultIfEmpty()
                        from n_i in db.News_Image
                        where n_i.news_id == n.id
                        select i).ToList(),

              Tags = (from t in db.Tags.DefaultIfEmpty()
                      from n_t in db.News_Tag
                      where n_t.news_id == n.id
                      select t).ToList(),

              Categories = (from c in db.Categories.DefaultIfEmpty()
                            from n_c in db.News_Category
                            where n_c.news_id == n.id
                            select c).ToList()
          }).ToList();

但是有多余的记录。

Answer 1

我决定使用第一个视图模型。

(from n in db.News
 select new NewsExt()
 {
    News = n,
    Images = (from i in db.Images.DefaultIfEmpty()
              join n_i in db.News_Image on i.id equals n_i.image_id
              where n_i.news_id == n.id
              select i).ToList(),

     Tags = (from t in db.Tags.DefaultIfEmpty()
             join n_t in db.News_Tag on t.id equals n_t.tag_id
             where n_t.news_id == n.id
             select t).ToList(),

      Categories = (from c in db.Categories.DefaultIfEmpty()
                    join n_c in db.News_Category on c.id equals n_c.category_id
                    where n_c.news_id == n.id
                    select c).ToList()
              }).ToList();

默认为一对多

1 个答案: