Question

我正在尝试在以下对象之间创建多对多关系：

public class Classified{
    [Key]
    public int Id {get;set;}    
    public string details {get;set;}
    public ICollection<ClassifiedRating> Ratings {get;set;}  
}

public class User{
    [Key]
    public int Id {get;set;}
    public string Name {get;set;}
}

public class ClassifiedRating{
    [Key]
    public User Rater {get;set;}
    [Key]
    public Classified Classified {get;set;}
    public int rating {get;set;}
}

运行时收到以下错误：

One or more validation errors were detected during model generation:

\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'ClassifiedRating' 
has no key defined. Define the key for this EntityType.

\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'ClassifiedRating'
 is based on type 'RateUser' that has no keys defined.

（“\ t”也出现在错误信息中，虽然我怀疑它是否相关，但它有点奇怪......）

Answer 1

据我所知，密钥必须是字符串，整数类型或Guid对象。基本上这会迫使你总是为你想要存储的每个类都有一个人工键，但通常这是一个好主意。尝试给ClassifiedRating一个整数键，而不是尝试使用类User。

Answer 2

ClassifiedRating应如下所示：

public class ClassifiedRating
{
    [Key, Column(Order = 0)]
    public int RaterId { get; set; }

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

    public User Rater {get;set;}
    public Classified Classified { get; set; }

    public int rating { get; set; }
}

命名约定将检测复合主键的两个部分作为其他两个表的外键，您应该在模型中获得所需的两个一对多关系。

实体框架代码首先通过DataAnnotations实现多对多关系

2 个答案: