NHibernate unidirectional one-to-one mapping problem.

**edurazee** · Jan 25 '10, 04:42 PM

I am trying to create a Unidirectional one-to-one relationship using NHibernate.

Example: An Order is given by a Customer.

Code:

Customer{ID, Name, Address}
OrderN{ID, Customer, OrderDate}

Here, OrderN.Customer-field is intended to store Customer.ID as an FK. And this field doesn't have any unique constraint.

(The OrderN-table is given such a name to avoid SQL keyword conflict.)

Customer.sql

Code:

------------
CREATE TABLE [dbo].[Customer](
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[Name] [varchar](50) NULL,
	[Address] [varchar](50) NULL,
 CONSTRAINT [PK_Customer] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

Customer.cs

Code:

-----------
public class Customer
{
	private int _id;
	public virtual int ID
	{
		get { return _id; }
		set { _id = value; }
	}

	private string _name;
	public virtual string Name
	{
		get { return _name; }
		set { _name = value; }
	}

	private string _address;
	public virtual string Address
	{
		get { return _address; }
		set { _address = value; }
	}
}

Customer.hbm.xm l

Code:

----------------
<?xml version="1.0" encoding="utf-8" ?>

<hibernate-mapping
  xmlns="urn:nhibernate-mapping-2.2"
  >
  <class name="NHibernate__One_To_One__Order_Customer.BO.Customer, NHibernate__One_To_One__Order_Customer.BO" table="Customer">
    <id name="ID" >
      <generator class="native" />
    </id>
    <property name="Name" column="Name" />      
    <property name="Address" column="Address" />
  </class>
</hibernate-mapping>

OrderN.sql

Code:

---------
CREATE TABLE [dbo].[OrderN](
	[ID] [int] IDENTITY(1,1) NOT NULL,
	[Customer] [int] NULL,
	[OrderDate] [datetime] NULL,
 CONSTRAINT [PK_Order] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
ALTER TABLE [dbo].[OrderN]  WITH CHECK ADD  CONSTRAINT [FK_Order_Customer] FOREIGN KEY([Customer])
REFERENCES [dbo].[Customer] ([ID])
GO
ALTER TABLE [dbo].[OrderN] CHECK CONSTRAINT [FK_Order_Customer]

OrderN.cs

Code:

---------
public class OrderN
{
	private int _id;
	public virtual int ID
	{
		get { return _id; }
		set { _id = value; }
	}

	private Customer _customer;
	public virtual Customer Customer
	{
		get { return _customer; }
		set { _customer = value; }
	}

	private DateTime _orderDate;
	public virtual DateTime OrderDate
	{
		get { return _orderDate; }
		set { _orderDate = value; }
	}
}

OrderN.hbm.xml

Code:

--------------

<?xml version="1.0" encoding="utf-8" ?>

<hibernate-mapping 
    xmlns="urn:nhibernate-mapping-2.2" 
    >
  <class name="NHibernate__One_To_One__Order_Customer.BO.OrderN, NHibernate__One_To_One__Order_Customer.BO" table="OrderN">
    <id name="ID">      
      <generator class="native" />
    </id>
    <property name="OrderDate" column="OrderDate"/>


    <one-to-one
        name="Customer"
        class="NHibernate__One_To_One__Order_Customer.BO.Customer, NHibernate__One_To_One__Order_Customer.BO" />


  </class>
</hibernate-mapping>

Main-program

Code:

------------
OrderN o = new OrderN();
o.OrderDate = DateTime.Now;
o.Customer = new Repository<Customer>().Get<Customer>(1);

Repository<OrderN> rep = new Repository<OrderN>();
rep.Save(o);

The problem is, After executing this c# code, OrderN.Customer-field is storing a null value.

But it was supposed to store the ID of the Customer. I.e. 1.

How to solve this problem?