c# - Entity Framework Code First 通过 DataAnnotations 实现多对多关系

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;}
}       

运行时出现以下错误:

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”也出现在错误消息中，虽然我怀疑它是否相关，但它有点奇怪....)

Answer 1

据我所知，键必须是字符串、整数类型或 Guid 对象。基本上，这会迫使您始终为每个要存储的类设置一个人工 key ，但通常这是个好主意。尝试给 ClassifiedRating 一个整数键，而不是尝试使用类 User。