实体框架代码首先是自我参考问题 [英] Entity framework code first self reference Problem

问题描述

i有一个评论表，其中每条评论都可能有评论类型的回复。

i mean评论表引用自己（我的英语不够好）。

还有一个文章表女巫有一系列评论。



每件事都没问题，记录正确插入数据库购买时我想检索特定评论的儿童评论>>他们是空的！ >>

请看一下代码...



这是我的课程：

Hi,
i have a Comment Table where every comment may have replies of type Comment.
i mean Comment Table is referencing its self(my english isnt good enough).
also there is an Article table witch has a collection of comments.

every thing is ok and records are inserted correctly into database buy when i want to retrieve child comments of a specific comment >> they`r null !! >>
take a look at code please...

here is my classes:

public class Comment
{
    public Comment()
    {
        this.Replies = new HashSet<Comment>();
    }

    public long Id { get; set; }
    public string Title { get; set; }

    public ICollection<Comment> Replies { get; set; }

    public long? ArticleId { get; set; }
    public Article Article { get; set; }
}


public class Article
{
    public Article()
    {
        this.Comments = new HashSet<Comment>();
    }

    public long Id { get; set; }
    public string Title { get; set; }

    public ICollection<Comment> Comments { get; set; }
}

及上下文：

and the context:

public class CommentContext : DbContext
{
    public CommentContext()
        : base("Default")
    {
    }

    public DbSet<Article> Articles { get; set; }
    public DbSet<Comment> Comments { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Article>()
                    .HasMany(a => a.Comments)
                    .WithOptional(c => c.Article)
                    .HasForeignKey(c => c.ArticleId);

        base.OnModelCreating(modelBuilder);
    }
}

一切正常，记录正确插入到数据库中代码：

every thing is ok and records are inserted correctly into database with this code:

CommentContext db = new CommentContext();

Article article = new Article() { Title = "Intro to .NET" };

Comment comment = new Comment() { Title = "Main Comment" };
comment.Replies.Add(new Comment() { Title = "Child comment 1" });
comment.Replies.Add(new Comment() { Title = "Child comment 2" });

article.Comments.Add(comment);
db.Articles.Add(article);
db.SaveChanges();

但是我无法回复孩子对评论的评论，以下是代码：

but i cant retrive child comments of a comment , here is the code for that:

Article article = db.Articles.Include("Comments").SingleOrDefault();
            foreach (var comment in article.Comments)
            {
                Console.WriteLine("Parent Comment: " + comment.Title);
                foreach (var reply in comment.Replies)
                {
                    Console.WriteLine(reply.Title);
                }
            }

看不到评论的回复..

非常感谢...

cant see the replies of the comment..
thanks alot...

推荐答案

我发现...

i必须做两个查询：

首先查询获取文章和第二个一个得到评论和回复。

i found that...
i have to do two query:
first query to get article and the second one to get the comments and replies.

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