entity-framework - Entity Framework 4.1 无效的列名

Question

我有两个表 News 和 NewsComments。我遵守命名规则

结构新闻评论

public class NewsComment : BaseComment
{
    public int NewsId { get; set; }

    public virtual News News { get; set; }      
}

但查询返回异常无效的列名“News_Id”。我知道这个异常在表中不相关的列中创建了什么。

CREATE TABLE [dbo].[NewsComments](
[Id] [int] IDENTITY(1,1) NOT NULL,
[NewsId] [int] NOT NULL,
[Text] [varchar](max) NOT NULL,
[UserId] [int] NOT NULL,
[CommentDate] [datetime] NOT NULL,
[Ip] [varchar](40) NOT NULL, CONSTRAINT [PK_NewsComments] PRIMARY KEY CLUSTERED([Id] ASC )WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]) ON [PRIMARY]

基础评论

public abstract class BaseComment : BasePersistentEntity, IComment
{

    public int UserId { get; set; }

    public virtual BaseUser User { get; set; }

    [Display(ResourceType = typeof(FrameworkResurce), Name = "CommentText")]
    public string Text { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "CommentDate")]
    public DateTime CommentDate { get; set; }


    public string Ip { get; set; }
}

新闻

public class News : BaseContent
{
    [Display(ResourceType = typeof(NewsResurce), Name = "NewsImage")]
    public string NewsImage { get; set; }

    public virtual ICollection<NewsCommentView> CommentViews { get; set; }
}

基本内容

public abstract class BaseContent : BasePersistentEntity
{
    [Display(ResourceType = typeof(FrameworkResurce), Name = "Keywords")]
    public string Keywords { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "TitleTranslit")]
    public string TitleTranslit { get; set; }

    [Required(ErrorMessageResourceType = typeof(FrameworkResurce), ErrorMessageResourceName = "IsTextEmpty")]
    [Display(ResourceType = typeof(FrameworkResurce), Name = "Title")]
    public string Title { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "Description")]
    public string Description { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "Contents")]
    public string Contents { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "DatePublish")]
    public DateTime DatePublish { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "AuthorPublish")]
    public string AuthorPublish { get; set; }

    [Display(ResourceType = typeof(FrameworkResurce), Name = "Author")]
    public string Author { get; set; }

    [Display(ResourceType = typeof(FrameworkResurce), Name = "AuthorUrl")]
    public string AuthorUrl { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "Views")]      
    public int Views { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "Comments")]
    public int Comments { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "IsComment")]
    public bool IsComment { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "SumVote")]
    public int SumVote { get; set; }


    [Display(ResourceType = typeof(FrameworkResurce), Name = "VoteCount")]
    public int VoteCount { get; set; }

    [NotMapped]
    [Display(ResourceType = typeof(FrameworkResurce), Name = "Rating")]
    public double Rating
    {
        get
        {
            if (VoteCount > 0)
            {
                return Math.Round((float)SumVote/VoteCount, 2);
            }

            return 0;
        }
    }
}

查询

private IEnumerable<NewsComment> GetComments()
    {
        var news = NewsCommentRepository.AllIncluding(c=>c.User,c=>c.News);
        return news;
    }

private DataRepository<NewsComment> NewsCommentRepository
        {
            get { return DataRepository<NewsComment>.Repository; }
        }

数据存储库

public class DataRepository<T> where T : BasePersistentEntity
{
    public static DataRepository<T>  Repository
    {
        get
        {
            return new DataRepository<T>();
        }
    }

    private readonly SGNContext<T> context = new SGNContext<T>();

    public IQueryable<T> All
    {
        get { return this.context.Table; }
    }

    public IQueryable<T> AllIncluding(params Expression<Func<T, object>>[] includeProperties)
    {
        IQueryable<T> query = this.context.Table;
        return includeProperties.Aggregate(query, (current, includeProperty) => current.Include(includeProperty));
    }

    public T Find(int id)
    {
        return this.context.Table.Find(id);
    }

    public void InsertOrUpdate(T country)
    {
        if (country.Id == default(int))
        {
            // New entity
            this.context.Table.Add(country);
            Save();
        }
        else
        {
            // Existing entity
            this.context.Entry(country).State = EntityState.Modified;
            Save();
        }
    }

    public void Delete(int id)
    {
        var country = this.context.Table.Find(id);
        this.context.Table.Remove(country);
        this.Save();
    }

    private void Save()
    {
        this.context.SaveChanges();
    }
}

在哪里使用 GetComments

    [GridAction]
    public ActionResult AjaxCommentsBinding()
    {
        return View(new GridModel<NewsComment>
        {
            Data = GetComments()
        });
    }

新闻评论浏览次数

CREATE VIEW [dbo].[NewsCommentViews]
AS
SELECT     dbo.NewsComments.NewsId, dbo.NewsComments.Text, dbo.NewsComments.UserId, dbo.NewsComments.CommentDate, dbo.NewsComments.Ip, 
                      dbo.Roles.RoleName, dbo.Users.UserName, dbo.Users.DateRegistered, dbo.NewsComments.Id, dbo.Users.Avatar
FROM         dbo.NewsComments INNER JOIN
                      dbo.Users ON dbo.NewsComments.UserId = dbo.Users.Id INNER JOIN
                      dbo.Roles ON dbo.Users.RoleId = dbo.Roles.Id

新闻评论浏览次数

[Table("NewsCommentViews")]
    public class NewsCommentView : NewsComment
    {
        public string RoleName { get; set; }

        public string UserName { get; set; }

        public DateTime DateRegistered { get; set; }

        public string Avatar { get; set; }
    }

Answer 1

问题在于News之间的关系和 NewsCommentView : 关系的一端是News.CommentViews收藏。但另一端是不是 NewsCommentView.News正如您所期望的那样。为什么？因为属性(property)News不是 声明 在 NewsCommentView类但在基类 NewsComment .现在 EF 不允许实体参与具有不是 的导航属性的关系。声明 在该实体类本身上，但仅在基类中。

因此，因为您没有 Fluent 映射，所以 EF 仅按约定定义所有关系。发生什么了？

News有导航属性 CommentViews声明并指向 NewsCommentView类(class)。

EF 未找到类型为 News 的逆属性这是 声明 在 NewsCommentView类(class)。 (有一个，但它在基类中，这不算数。)

因此，EF 假设关系的另一端是 未曝光 在 NewsCommentView类(class)。

未公开意味着:EF 没有导航属性也没有外键属性，并且将假定数据库表/ View 中必要的外键列NewsCommentViews将有一个标准的约定名称。

这个约定俗成的名字是 NameOfEntityClass_PKPropertyName -> News_Id

您在 View 中的真实姓名是 NewsId尽管。因此，EF 查询列 News_Id不存在，因此异常(exception)。

当你的MVC-View访问 NewsComment.News.CommentViews时，该异常可能是由于延迟加载而触发的。 .

您可以通过在 Fluent API 中明确指定 FK 列名来解决此问题(据我所知，没有 Fluent 映射就没有其他方法):

public class MyContext : DbContext
{
    // ...

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<News>()
            .HasMany(n => n.CommentViews)
            .WithRequired() // <- no param because not exposed end of relation,
                            // nc => nc.News would throw an exception
                            // because nc.News is in the base class
            .Map(a => a.MapKey("NewsId"));
    }
}

但是 小心 : 请注意 NewsCommentView.News是 不是 属于 News.CommentViews的关系的另一端.这意味着如果您有 NewsCommentView在您的 News.CommentViews然后收藏 NewsCommentView.News 不是 回到那个 News目的。另一端是不可见的，不会暴露在模型中。上面的映射只是修复了 FK 列名问题，但不会改变约定会创建的关系(除非可能将关系更改为必需而不是可选)。