引用/有一个映射通过3个表

问题描述

我的模型对象阅读有一个位置，但它不是数据库中的直接关系。在DB中，这个有-a关系或引用跨越了3个表格，如下所示：

阅读

>映射到ComponentReading表，我希望我的 Location 映射到Location表。

  public class ReadingMap：ClassMap< Reading> 
 {
 public ReadingMap（）
 {
 Table（ComponentReading）; 
 Id（x => x.ID）.Column（ComponentReadingId）; 
 
参考（x => x.Location）.Formula（
 Join（VehicleReading，vr => 
 {
 Join（TrainReading ，tr => 
 {
 tr.References（x => x.Location，LocationId）; 
}）; 
}）; 
 
 Map（x => x.TemperatureValue）.Column（Temperature）; 
} 
} 
  

以下是简单的位置映射：

  public class LocationMap：ClassMap< Location> 
 {
 public LocationMap（）
 {
 Id（x => x.ID）.Column（ LocationId）; 
 Map（x => x.Name）; 
} 
} 
  

引用（方法排序显示了我想用读取和 Location ，但是显然我不能像FNH那样向FNH表示我不认为加入（）代码甚至几乎是正确的，但它也是试图传达我之后的关系。

我希望有人能看到我在这里想要做什么。你能帮我吗？

解决方案

我认为你不能这样嵌套连接。一个丑陋但实用的解决方案将是（未经测试）：

$ $ p $ $ $ $ {get;组; }

保护虚拟Hidden.TrainReading m_trainReading;

public virtual Location Location
{get {return m_trainReading.Location; } set {m_trainReading.Location = value; }}

public virtual int TemperatureValue {get;组; }


$ b命名空间隐藏
{
class TrainReading
{
public virtual int ID {get;组; }
public virtual int VehicleReadingId {get;组; }
public virtual Location Location {get;组; }
}
}

public class ReadingMap：ClassMap< Reading>
{
public ReadingMap（）
{
Table（ComponentReading）;
Id（x => x.ID）.Column（ComponentReadingId）;

参考文献（Reveal.Member< Reading，Hidden.TrainReading>（m_trainReading），）;

Map（x => x.TemperatureValue）.Column（Temperature）;
}
}

public class TrainReadingMap：ClassMap< Hidden.TrainReading>
{
公共TrainReadingMap（）
{
表（TrainReading）;
Id（x => x.ID）.Column（TrainReadingId）;

参考文献（x => x.Location，LocationId）;

Join（VehicleReading，vr =>
{
vr.KeyColumn（TrainReadingId）;
vr.Map（x => x。 VehicleReadingId，VehicleReadingId）;
}）;
}
}

My model object Reading has a Location but it's not a direct relationship in the database. In the DB, this "has-a" relationship or "reference" spans 3 tables, as shown in this snip:

My Reading maps to the ComponentReading table and i want my Location to map to the Location table. My ClassMap<Reading> class looks like this for now:

public class ReadingMap : ClassMap<Reading>
{
    public ReadingMap()
    {
        Table("ComponentReading");
        Id(x => x.ID).Column("ComponentReadingId");

        //References(x => x.Location).Formula(
        Join("VehicleReading", vr =>
            {
                Join("TrainReading", tr =>
                    {
                        tr.References(x => x.Location, "LocationId");
                    });
            });

        Map(x => x.TemperatureValue).Column("Temperature");
    }
}

And here is my simple Location mapping:

public class LocationMap : ClassMap<Location>
{
    public LocationMap()
    {
        Id(x => x.ID).Column("LocationId");
        Map(x => x.Name);
    }
}

The commented References( method sort of shows what i want to achieve with the relationship between Reading and Location but obviously i can't express it to FNH as simply as the commented line suggests.

I don't think the Join( code is even nearly correct either, but it also tries to communicate the relationship that i'm after.

I hope someone can see what i'm trying to do here. Can you help me?

This question is related.

解决方案

I think you cant nest joins that way. An ugly but pragmatic solution would be (untested):

class Reading
{
    public virtual int ID { get; set; }

    protected virtual Hidden.TrainReading m_trainReading;

    public virtual Location Location
    { get { return m_trainReading.Location; } set { m_trainReading.Location = value; } }

    public virtual int TemperatureValue { get; set; }

}

namespace Hidden
{
    class TrainReading
    {
        public virtual int ID { get; set; }
        public virtual int VehicleReadingId { get; set; }
        public virtual Location Location { get; set; }
    }
}

public class ReadingMap : ClassMap<Reading>
{
    public ReadingMap()
    {
        Table("ComponentReading");
        Id(x => x.ID).Column("ComponentReadingId");

        References(Reveal.Member<Reading, Hidden.TrainReading>("m_trainReading"), "");

        Map(x => x.TemperatureValue).Column("Temperature");
    }
}

public class TrainReadingMap : ClassMap<Hidden.TrainReading>
{
    public TrainReadingMap()
    {
        Table("TrainReading");
        Id(x => x.ID).Column("TrainReadingId");

        References(x => x.Location, "LocationId");

        Join("VehicleReading", vr =>
        {
            vr.KeyColumn("TrainReadingId");
            vr.Map(x => x.VehicleReadingId, "VehicleReadingId");
        });
    }
}

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