基于外键 EF 的主键

Question

一开始试过，如下，还是没有结果：

Defining two foreign keys as primary key in Entity Framework
Entity Framework Two foreign keys as primary key

这是我的实体：

public class Passage
{
        [Key, ForeignKey("FromID")]
        public Localization From { get; set; }

        public int ToID { get; set; }

        [Key, ForeignKey("ToID")]
        public Localization To { get; set; }

        [Required]
        public string HourForm { get; set; }

        [Required]
        public string HourTo { get; set; }

        [Required]
        public int Seats { get; set; }

        [Required]
        public char Weekend { get; set; }

        public int? AdditinalTime { get; set; }

        public int FromID { get; set; }
}

我正在尝试基于两个外键创建主键。有错误

EntityType 'Passage' has no key defined. Define the key for this EntityType.

我做错了什么？

Answer 1

作为引用之一 links said, you need to use the Column attribute to specify the order of your composite keys:

public class Passage
{
    [Key,Column(Order=0), ForeignKey("From")]
    public int FromId { get; set; }

    [Key,Column(Order=1), ForeignKey("To")]
    public int ToId { get; set; }
    //...
}

我现在注意到您在导航属性上使用了这些属性，正如@PaulAbbott 在他的回答中所说，在这种情况下，必须使用 标量属性 定义主键, FK 属性。

Answer 2

直接引用您的第一个 link:

"Primary keys always must be defined by scalar properties in the entity class. You cannot refer to the PKs by navigation properties alone."

因此，您需要将关键属性放在标量值上，而不是导航属性。

public class Passage
{
    [Key, ForeignKey("From"), Column(Order = 0)]
    public int FromID { get; set; }

    public Localization From { get; set; }

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

    public Localization To { get; set; }
}

基于外键 EF 的主键

Primary Key based on Foreign Keys EF

sql-server

entity-framework

ef-code-first