EF代碼與各種父母的第一個關係0/1到0/1

Question

EF CodeFirst和關係0/1到0/1有一些問題。我有3個「表」，其中包含另一個，這是可選的。

它類似於：

[DataContract] 
public class A 
{ 
    [DataMember, Key] 
    public int Id {get;set;} 
    [DataMember] 
    public int? IdD 
    [ForeignKey("idD")] 
    public virtual D D {get; set;} 
} 
[DataContract] 
public class B 
{ 
    [DataMember, Key] 
    public int Id {get;set;} 
    [DataMember] 
    public int? IdD 
    [ForeignKey("idD")] 
    public virtual D D {get; set;} 
} 
[DataContract] 
public class C 
{ 
    [DataMember, Key] 
    public int Id {get;set;} 
    [DataMember] 
    public int? IdD 
    [ForeignKey("idD")] 
    public virtual D D {get; set;} 
}  
[DataContract] 
public class D 
{ 
    [DataMember, Key] 
    public int Id {get;set;} 

    public virtual A A { get; set; } 
    public virtual B B { get; set; } 
    public virtual C C { get; set; } 
} 

當我嘗試做的遷移，出現錯誤：

 
Unable to determine the principal end of an association between the types 'XXXXXX' and 'XXXXXX'. 
The principal end of this association must be explicitly configured using either the relationship 
fluent API or data annotations. 

我嘗試用DataAnnotations和Fluent API，並出現相同的錯誤。在流利的API我嘗試：

與A，B或C類

 this.HasOptional(casv => casv.D) 
      .WithOptionalDependent(e => e.A)//I try with denendent and Principal 
      .Map(m => m.MapKey("IdD")) // I try without this 
      .WillCascadeOnDelete(true); 

Answer 1

試試這個，我認爲這是更好看的比你的代碼：

this.HasOptional(casv => casv.D) 
    .WithOptionalDependent(e => e.A) 
    .Map(m => m.MapKey("IdD")) 
    .WillCascadeOnDelete(true);