如何創建複合外鍵的表，複合主鍵

Question

我有兩個表具有複合主鍵：

public class Event 
{ 
    [Key] 
    [Column(Order = 1)] 
    public string ID1 { get; set; } 

    [Key] 
    [Column(Order = 2)] 
    public int ID2 { get; set; } 
    public DateTime EventDate { get; set; } 
    public string DocID1 { get; set; } 
    public int DocID2 { get; set; } 

}

public class EventDocument 
{ 
    [Key] 
    [Column(Order = 1)] 
    public string ID1 { get; set; } 
    [Key] 
    [Column(Order = 2)] 
    public int ID2 { get; set; } 

    public string Name { get; set; } 
    public string SurName { get; set; } 
    public string Number { get; set; } 

    public virtual ICollection<Event> Events { get; set; } 
} 

我需要創建Event複合外鍵表格到EventDocument表格

我試過像這樣創建FK

類的事件：

[ForeignKey("DocID1")] 
[Column(Order = 0)] 
public string DocID1 { get; set; } 

[ForeignKey("DocID2")] 
[Column(Order = 1)] 
public string DocID2 { get; set; } 

但我得到一個錯誤：

The property 'DocID1' cannot be configured as a navigation property. The property must be a valid entity type and the property should have a non-abstract getter and setter. For collection properties the type must implement ICollection where T is a valid entity type."}

我不明白了什麼，我做錯了

Answer 1

複合外鍵要求ForeignKey要應用屬性在導航屬性中指定外鍵屬性名稱的逗號分隔列表：

If you add the ForeignKey attribute to a foreign key property, you should specify the name of the associated navigation property. If you add the ForeignKey attribute to a navigation property, you should specify the name of the associated foreign key(s). If a navigation property has multiple foreign keys, use comma to separate the list of foreign key names.

既然你在Event類沒有導航屬性，則應它適用於相應的導航性能在EventDocument類：

[ForeignKey("DocID1, DocID2")] 
public virtual ICollection<Event> Events { get; set; } 

和問題應該得到解決。

但我個人發現與Fluent API建立關係要容易理解，並且不易出錯。舉例來說，同樣可以通過以下流利的配置來實現：

modelBuilder.Entity<EventDocument>() 
    .HasMany(e => e.Events) 
    .WithRequired() // or .WithOptional() 
    .HasForeignKey(e => new { e.DocID1, e.DocID2 }); 

順便說一句相同的複合材料的PK（而不是所有這些Key/Column(Order = ...)屬性）：

modelBuilder.Entity<Event>() 
    .HasKey(e => new { e.ID1, e.ID2 }); 

modelBuilder.Entity<EventDocument>() 
    .HasKey(e => new { e.ID1, e.ID2 });