使用Entity Framework加入3个表

How can I build a model using Entity Framework to join 3 tables?

如何使用Entity Framework构建模型来连接3个表？

At the moment I have:

目前我有：

public class KeywordAdCategory
{
    [Key]
    [Column("Keyword_Id", Order = 0)]
    public int Keyword_Id { get; set; }

    [Key]
    [Column("Ad_Id", Order = 1)]
    public int Ad_Id { get; set; }

    [Key]
    [Column("Category_Id", Order = 2)]
    public int Category_Id { get; set; }
}

But I don't have any navigation properties.

但我没有任何导航属性。

Is there a better way to build a relashionship between 3 tables using Entity Framework?

有没有更好的方法使用Entity Framework在3个表之间建立关系？

Also the Keyword, Ad and Category models:

关键字，广告和类别模型：

public class Keyword
{
    public int Id { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Address> Addresses { get; set; }
}

public class Ad
{
    // Primary properties
    [Key]
    public int Id { get; set; }

    // Navigation properties
    public AdOperation AdOperation { get; set; }
    public Member Member { get; set; }
    public Address Address { get; set; }
    public Category Category { get; set; }

    public virtual ICollection<Picture> Pictures { get; set; }

    private ICollection<Feature> _features;
    public virtual ICollection<Feature> Features
    {
        get { return _features ?? (_features = new HashSet<Feature>()); }
        set { _features = value; }
    }
}

public class Category
{
    // Primary properties
    public int Id { get; set; }
    public int? CategoryParent_Id { get; set; }
    public int? CategoryGroup_Id { get; set; }
    public bool IsActive { get; set; }

    // Navigation properties
    public Keyword Keyword { get; set; }
}

Thanks.

谢谢。

1 个解决方案

#1

I'm assuming that you're using Code-First Entity Framework here, and that you have your KeywordAdCategory object in your database as well. In which case, just simply do the following in your KeywordAdCategory class to do the proper mapping:

我假设你在这里使用Code-First Entity Framework，并且你的数据库中也有你的KeywordAdCategory对象。在这种情况下，只需在KeywordAdCategory类中执行以下操作即可进行正确的映射：

[Key, ForeignKey("Keyword")]
[Column("Keyword_Id", Order = 0)]
public int Keyword_Id { get; set; }

[Key, ForeignKey("Ad")]
[Column("Ad_Id", Order = 1)]
public int Ad_Id { get; set; }

[Key, ForeignKey("Category")]
[Column("Category_Id", Order = 2)]
public int Category_Id { get; set; }

public virtual Keyword Keyword { get; set; }

public virtual Ad Ad { get; set; }

public virtual Category Category { get; set; }

Doing this should do the proper mappings, put FKs on your KeywordAdCategory table, and thus give you the ability to have good navigation properties to the other objects.

这样做应该进行正确的映射，将FK放在KeywordAdCategory表上，从而使您能够为其他对象提供良好的导航属性。