Entity Framework Core 使用 Include on QueryType(Database View) [英] Entity Framework Core Use Include on QueryType(Database View)

问题描述

我将 EF Core 连接到 MySql 并且我有一个名为的视图:

<块引用>

帖子视图

我读了这篇

PostView 拥有 Post 中的所有属性(id、标题、内容、评论等)，另外还有一个名为:Views 的列，显示有多少人阅读了这篇文章.

<小时>

这是我的帖子:

公共部分类 Post{公共邮政(){Comment = new HashSet();}公共字符串 ID { 获取；放;}公共字符串 ApartmentId { 获取；放;}公共字符串 AuthorId { 获取；放;}公共字符串 CategoryId { 获取；放;}公共字符串标题{获取；放;}公共字符串 描述 { 获取；放;}公共日期时间?截止日期{得到;放;}公共布尔?禁用 { 获取;放;}公共日期时间?CreatedAt { 获取;放;}公共日期时间?更新在 { 获取；放;}公共字符串 UpdatedBy { 获取；放;}公共虚拟公寓公寓{get;放;}公共虚拟用户作者{ get;放;}公共虚拟 PostCategory Category { get;放;}}公共虚拟 ICollection评论 { 得到;放;}}

PostWithViews 类与 Post 几乎相同，但多了 1 个属性 Views:

public int Views { get;放;}

这是我如何包含属性，例如评论:

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，如比较查询类型与实体类型 文档主题:

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• 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 而言并非如此，因此不能用于 Include/ThenInclude(或 LINQ to Entities 查询).

但是Apartment、Author 和Category 是指向实体的参考导航属性"，所以它们应该功能齐全.

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.

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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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