引用EF中的导航属性的父表 [英] Reference a parent table for a Navigation Property in EF

问题描述

我基本上有三张表与FK的

I essentially have three tables with FK's

Make

• MakeId


• MakeName

模型

• ModelId


• ModelName


• MakeId（FK）

车辆

• VehicleId


• DatePurchased


• ModelId（FK）

我想要一个导航属性从车辆到Make而不修改我的数据库

I would like a navigation property from Vehicle to Make without modifying my database

我试过：

public class Make
{
    public int MakeId {get;set;}
    <snip>...</snip>
    public virtual Vehicle Vehicles {get;set;}

}

<snip>Model</snip>

public class Vehicle
{
    public int VehicleId {get;set}
    <snip>...</snip>
    public virtual Make VehicleMake {get;set;}
}


public class VehicleMap : EntityTypeConfiguration<Vehicle>
{
    public VehicleMap()
    {
        this.HasKey(t => t.VehicleId);
        <snip>...</snip>
        this.HasRequired(t => t.VehicleMake)
        .WithMany(t => t.Vehicles)
        .HasForeignKey(t => t.Model.MakeId);
    }

}

但是当我这样做一个例外：

However when I did this I received an exception:

属性表达式'd => d.Model.MakeId'无效。
表达式应该表示一个属性：C＃：'t => t.MyProperty'
VB.Net：'Function（t）t.MyProperty'。当指定多个
属性时，使用匿名类型：C＃：'t => new {t.MyProperty1，
t.MyProperty2}'VB.Net：'Function（t）New From {t.MyProperty1，
t.MyProperty2}'。

The properties expression 'd => d.Model.MakeId' is not valid. The expression should represent a property: C#: 't => t.MyProperty' VB.Net: 'Function(t) t.MyProperty'. When specifying multiple properties use an anonymous type: C#: 't => new { t.MyProperty1, t.MyProperty2 }' VB.Net: 'Function(t) New From { t.MyProperty1, t.MyProperty2 }'.

如何在我的Make&车载表不添加Vehicle.ModelId列到我的数据库？

How can I create a navigation property on my Make & Vehicle tables without adding Vehicle.ModelId column to my database?

推荐答案

EF不支持这种类型的建模。您可以创建一个围绕 Model.Make 的财产，如下所示。但是它可能会导致不必要的懒惰加载。

EF does not support that type of modeling. You can create a property that wraps around Model.Make as follows. But it may lead to unnecessary lazy loading.

public class Vehicle
{
    public int VehicleId {get;set}
    <snip>...</snip>

    [NotMapped]
    public virtual Make VehicleMake 
    {
        get { return Model.Make; }
        set { Model.Make = value; }
    }
}

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