Code First Entity Framework不会创建一对多关系

Question

So I have a class (Article) That is supposed to have a one-to-many relationship with another class (Category):

public class Article
{
  [Key]
  public int ArticleId { get; set;}

  public virtual List<Category> Categories { get; set; }
}

public class Category
{
  [Key]
  public int Id { get; set;}

  public string Caption { get; set;
}

When I had Code First build the Database, it generated Category having a one-to-one relationship with Article. This results in the the Category only being related to a single Article. Dropping and recreating the database still generates the issue. Any idea on what I'm doing wrong?

Answer 1

1) If your Article has many Category , but Categories has only one Article :

public class Article{
    private ICollection<Category> _CategoryList;
    public int ArticleId { get; set;}
    public virtual ICollection<Category> CategoryList {
        get { return _CategoryList = _CategoryList?? new HashSet<Category>(); }
        set { _CategoryList= value; }
    }
}

public class Category{
    public int Id { get; set;}
    public string Caption { get; set;}
    public Article Article { get; set;}
}

This sounds little inlogical for me.

2) If your Category has many Article , and Article has only one Category :

public class Article{
    public int ArticleId { get; set;}
    public Category Category { get; set;}
}

public class Category{
    private ICollection<Article> _ArticleList;
    public int Id { get; set;}
    public string Caption { get; set;}
    public virtual ICollection<Article> ArticleList {
        get { return _ArticleList= _ArticleList?? new HashSet<Article>(); }
        set { _ArticleList= value; }
    }
}

Note, you do not need [Key] in case there is keyword Id in the property name. EF treats the property as Key automatically.