实体框架核心使用QueryType（数据库视图）上的包含 [英] Entity Framework Core Use Include on QueryType(Database View)

问题描述

我已将EF Core连接到MySql，并且有一个名为：

PostViews

blockquote>

我阅读了此

PostView在Post中具有所有属性（ID，标题，内容，评论等）。 ，另外还有一列称为：查看显示了这篇文章的人数的视图。

---

这是我的帖子：

 公共部分类Post 
 {
 public Post（）
 {
 Comment =新的HashSet< Comment>（）; 
} 
 
公共字符串ID {get;组; } 
公用字串ApartmentId {get;组; } 
公用字串AuthorId {get;组; } 
公共字符串CategoryId {get;组; } 
公用字串Title {get;组; } 
公共字符串说明{get;组; } 
公共DateTime？ DueDate {获取；组; } 
公共布尔？残疾人{组; } 
公共DateTime？ CreatedAt {get;组; } 
公共DateTime？ UpdatedAt {get;组; } 
公共字符串UpdatedBy {组; } 
 
公共虚拟公寓公寓{组; } 
公共虚拟用户作者{get;组; } 
公共虚拟PostCategory类别{get;组; }} 
公共虚拟ICollection< Comment>评论{get;组; } 
} 
  

PostWithViews类与Post几乎相同，但具有1个以上的属性Views：

  public int Views {get;组; } 
  

以下是我如何添加属性的信息：注释：

 返回GetAll（）
 .Include（p => p.Author）
。 Include（p => p.Comment）
  

解决方案

当前（EF Core 2.x）查询类型不支持集合导航属性，如将查询类型与实体类型进行比较文档主题：

• 它们只能包含指向实体的参考导航属性。

因此，尽管您的 Comment 属性看起来像集合导航属性，但对于EF Core而言，它不是，因此不能在<$ c中使用$ c>包含 / 然后包含（或LINQ to Entities查询）。

但是公寓，作者和类别是 r指向实体的参考导航属性 ，因此它们应具有完整的功能。

I have EF Core connected to MySql and I have a View called:

PostViews

I read this article saying I can use Query Types for Database Views.

It works if I just call _context.PostViews, but if I use Include on it like:

_context.PostViews.Include(xxxx), it throws me this error:

System.InvalidOperationException: 'The property 'Comment' is not a navigation property of entity type 'PostWithViews'. The 'Include(string)' method can only be used with a '.' separated list of navigation property names.'

PostView has all properties in Post (id, title, content, Comment etc.), plus it has one extra column called: Views which shows how many people have read this post.

---

Here is my Post:

public partial class Post
    {
        public Post()
        {
            Comment = new HashSet<Comment>();
        }

        public string Id { get; set; }
        public string ApartmentId { get; set; }
        public string AuthorId { get; set; }
        public string CategoryId { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
        public DateTime? DueDate { get; set; }
        public bool? Disabled { get; set; }
        public DateTime? CreatedAt { get; set; }
        public DateTime? UpdatedAt { get; set; }
        public string UpdatedBy { get; set; }

        public virtual Apartment Apartment { get; set; }
        public virtual User Author { get; set; }
        public virtual PostCategory Category { get; set; }}
        public virtual ICollection<Comment> Comment { get; set; }
    }

PostWithViews class is almost the same with Post but with 1 more property Views:

public int Views { get; set; }

Here is how I include properties e.g. Comment :

return GetAll()
       .Include(p => p.Author)
       .Include(p => p.Comment)

解决方案

Currently (EF Core 2.x) query types do not support collection navigation properties, as mentioned in the Compare query types to entity types documentation topic:

• They can only contain reference navigation properties pointing to entities.

So although your Comment property looks like collection navigation property, for EF Core it s isn't, hence cannot be used in Include / ThenInclude (or LINQ to Entities query).

However Apartment, Author and Category are "reference navigation properties pointing to entities", so they should be fully functional.

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