与Fluent NHibernate一对一或零关系

Question

Given two tables:

 ___________
|Table1     |
|-----------|
|Id         |
|___________|
 ___________
|Table2     |
|-----------|
|Id         |
|Table1_Id  |
|___________|

Where Table2 record doesn't neccesserily have to exist (ie the relationship is One{Table1}-to-OneOrZero{Table2} ).

I need to be able to Save and Retrieve data from both tables using a parent class, which is mapped to Table1.

The entities are as follows:

public class Table1
{
   int Id {get; set;}
   Table2 Table2 {get; set;}
}
public class Table2
{
   int Id {get; set;}
}

...I've created the mappings as follows:

public class Table1Map
{
   this.Id(x => x.Id);
   HasOne(x => x.Table2).Cascade.All();
}

public class Table2Map
{
   this.Id(x => x.Id);
}

...which works fine for reading but not writing the data, because it tries to insert NULL into Table2.Table1_Id column instead of taking it from Table1.Id property.

Is there a way to make this work for inserts without having to create a bi-directional reference, ie without Table1 property on Table2 class ?

Answer 1

I have recently come across this question in SO. As far as relationship goes, as already mentioned by @Hacked it can't be HasOne because they are not sharing a common primary key. Consider using HasMany (not really sure) and missing part for unidirectional relationship is Not.KeyUpdate

public class Table1Map
{
   this.Id(x => x.Id);
   HasMany(x => x.Table2)
   .Not.KeyUpdate() <--here
   .Cascade.All();   
}

Below are the reference links

NHibernate configuration for uni-directional one-to-many relation

NHibernate still issues update after insert

Answer 2

Normally, you'd just uses References rather than HasOne . See I think you mean a many-to-one, sir .

Article summary: HasOne , or one-to-one relationship, is specifically for a relationship where the two tables share a primary key.