实体框架 - 定义不需要侧面的连接 [英] Entity framework - Define connection where neither side is required

问题描述

我有一个问题，我必须创建一个模型，我们有两个实体可以链接在一起，但也可以作为独立实体存在。

模型目前看起来像这样：

  public class授权
 {
 public int AuthorizationID {get;组; } 
 
 public virtual Change Change {get;组; 
} 
 
 
 public class更改
 {
 public int ChangeID {get;组; } 
 
 public virtual授权授权{get;组; } 
 
 public int？授权ID {get;组; } 
} 
  

原因是我们可以独立于更改和一些更改需要授权，有些不需要，所以双方都不需要关系。

我可以使用流畅的API来配置，如下所示：

  modelBuilder.Entity< Authorization>（）
 .HasOptional（t => t.Change）
 .WithOptionalPrincipal t => t.授权）; 
  

很好，除了它创建的迁移看起来像这样

  CreateTable（
dbo.Changes，
c => new 
 {
 ChangeID = c。 int（nullable：false，identity：true），
 AuthorizationID = c.Int（），
 Authorisation_AuthorisationID = c.Int（），
}）
 .PrimaryKey（t = > t.ChangeID）
 .ForeignKey（dbo.Authorisations，t => t.Authorisation_AuthorizationID）
 .Index（t => t.Authorisation_AuthorizationID）; 
  

EF正在决定要添加新列（ Authorisation_AuthorisationID ）为了使我作为两个实体之间的FK，我真正想要做的就是将change.AuthorizationID属性作为FK使用到Authorization，我找不到一种配置方式（请注意，我需要FK在模型中 - 与其他应用程序的一致性比其他任何东西一样）。

总而言之，我需要能够创建一个关系双方之间的关系是可选的，如果可能，我希望能够自己定义FK列。

我只是接近这个错误？我一直在盯着同一个代码块，这么长时间我可能会丢失一些简单的东西。

解决方案

看起来像显式的外键属性不支持一对一关系 - 没有 HasForeignKey Fluent API，如果你把 ForeignKey 属性导航属性你得到异常说多重性必须是 * 。

所以唯一的选择是删除显式的 Change.AuthorizationID 属性，只能使用导航属性：

型号：

  public class授权
 {
 public int AuthorizationID {get;组; } 
 public virtual Change Change {get;组; 
} 
 
 public class更改
 {
 public int ChangeID {get;组; } 
 public virtual Authorization {get;组; 
} 
  

配置：

  modelBuilder.Entity< Authorization>（）
 .HasOptional（t => t.Change）
 .WithOptionalPrincipal（t = > t.Authorisation）
 .Map（a => a.MapKey（AuthorizationID））; 
  

I have a problem, I have to create a model where we have two entities which CAN be linked together but can also exist as stand alone entities.

The model currently looks like this:

 public class Authorisation
 {
    public int AuthorisationID { get; set; }

    public virtual Change Change { get; set; }
}


public class Change
{
    public int ChangeID{ get; set; }

    public virtual Authorisation Authorisation { get; set; }

    public int? AuthorisationID{ get; set; }
}

The reason for this is that we can have an authorization record independent of a change, and some changes require authorisation and some dont, so neither side of the relationship is required.

I can configure this with the fluent API like so:

modelBuilder.Entity<Authorisation>()
        .HasOptional(t => t.Change)
        .WithOptionalPrincipal(t => t.Authorisation);

And alls well, Except that the migration that it creates looks like this

CreateTable(
            "dbo.Changes",
            c => new
                {
                    ChangeID = c.Int(nullable: false, identity: true),
                    AuthorisationID = c.Int(),
                    Authorisation_AuthorisationID = c.Int(),
                })
            .PrimaryKey(t => t.ChangeID)
            .ForeignKey("dbo.Authorisations", t => t.Authorisation_AuthorisationID)
            .Index(t => t.Authorisation_AuthorisationID);

EF is deciding that its going to add a new column (Authorisation_AuthorisationID) for me to use as the FK between the two entities, what I really want to be able to do is to use the change.AuthorisationID property as the FK onto the Authorisation, I cannot find a way to configure this at all (Please note that I need the FK to be in the model - for consistency with the rest of the app more than anything else).

To sum up I need to be able to create a relationship between two entities where both sides of the relationship are optional and if possible I want to be able to define the FK column myself.

Am I just approaching this wrong? Ive been staring at the same block of code for so long I could be missing something simple.

解决方案

Looks like explicit foreign key property is not supported for one-to-one relationships - there is no HasForeignKey Fluent API and also if you put ForeignKey attribute on the navigation property you get exception saying that multiplicity must be *.

So the only choice you have is to remove the explicit Change.AuthorisationID property and work only with navigation properties:

Model:

public class Authorisation
{
    public int AuthorisationID { get; set; }
    public virtual Change Change { get; set; }
}

public class Change
{
    public int ChangeID{ get; set; }
    public virtual Authorisation Authorisation { get; set; }
}

Configuration:

modelBuilder.Entity<Authorisation>()
    .HasOptional(t => t.Change)
    .WithOptionalPrincipal(t => t.Authorisation)
    .Map(a => a.MapKey("AuthorisationID"));

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