在EF7中加载参考 [英] Loading of references in EF7

问题描述

我有两个班级-作者和博客文章:

I'm having two classes - author and blogpost:

public class Author
{
    public Author()
    {
        Blogposts = new HashSet<Blogpost>();
    }

    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Blogpost> Blogposts { get; set; }
}

和

public class Blogpost
{
    public Blogpost()
    {
    }

    // Properties
    public int Id { get; set; }
    public string Text { get; set; }

    public int AuthorId { get; set; }

    public Author Author { get; set; }
}

使用EF7(beta4)，我通过以下方式进行连接:

Using EF7 (beta4), I'm connecting them the following way:

public partial class MyDbContext : DbContext
{
    public virtual DbSet<Author> Author { get; set; }
    public virtual DbSet<Blogpost> Blogpost { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Author>(entity =>
            {
                entity.Property(e => e.Id)
                    .ForSqlServer().UseIdentity();
            });

            modelBuilder.Entity<Blogpost>(entity =>
            {
                entity.Property(e => e.Id)
                    .ForSqlServer().UseIdentity();
            });

            modelBuilder.Entity<Blogpost>(entity =>
            {
                entity.Reference<Author>(d => d.Author).InverseCollection(p => p.Blogposts).ForeignKey(d => d.AuthorId);
            });
    }
}

当我访问博客文章Db.Blogpost.First(x => x.Id == id)时，我会检索博客文章对象-但是，.Author属性为null.另外，检索任何Author对象时，其.Blogposts集合为空.

When I access a blogpost Db.Blogpost.First(x => x.Id == id) I retrieve the Blogpost object - however, the .Author property is null. Also, when retrieving any Author object, it's .Blogposts collection is empty.

我知道EF7既没有实现预加载，也没有实现延迟加载.但是我该如何检索/分配通过外键引用的任何对象?

I understand the EF7 has neither implemented eager-loading nor lazy-loading yet. But how would I then retrieve/assign any objects referenced via foreign key?

推荐答案

EF 7已实现了预加载.

EF 7 has implemented eager loading.

使用.include

Use .Include

var post = context.Blogpost.First(); // post.Author will be null

var post = context.Blogpost.Include(b => b.Author).First(); // post.Author will be loaded

有关使用集合的更多信息，请参见以下问题的答案:如何使用集合

For more information on working with collections, see the answer to this question: How to work with collections

这篇关于在EF7中加载参考的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！