我有兩個課程 - 作者和博客:
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),我按以下方式連接它們:
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);
});
}
}
當我訪問博客帖子Db.Blogpost.First(x => x.Id == id)
檢索到博客帖子對象-然而,所述.Author
屬性為null。此外,在檢索任何Author對象時,它的.Blogposts
集合為空。
據我所知,EF7既未實現預先加載也未實現延遲加載。但是,我如何檢索/分配通過外鍵引用的任何對象?
EF 7實現了預先加載。
使用.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
有關使用集合的更多信息,請參閱此問題的答案: 如何使用集合