I've an issue using one-to-one mapping. I've searched internet and found many solutions but none was satisfying. Most of the examples carry overhead of storing parent instance in child class.

I want to use only parent Id in child class having foreign key constraint relationship but dont want to keep any parent instance in child.

When I try to load the records from database it throws exception "No row with the given identifier exists [AssemblyName.B#d6455522-6c6d-4582-b6fb-5ac5ce9551f6]". But, the record exists in Table "B" properly.

Any solutions for this issue?

The class structure:

class A
{
public virtual string Id {get;set;}
public virtual B _B_ {get;set;}
// properties......
}

class B
{
public virtual string Id {get;set;}
// properties......
public virtual string ParentId { get;set;} // class A Id
}

The database structure:

CREATE TABLE [A](
[Id] [nvarchar](45) NOT NULL
///....
CONSTRAINT [PK__A__00000000000002C0] 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]

CREATE TABLE [B](
[Id] [nvarchar](45) NOT NULL,
[ParentId] [nvarchar](45) NOT NULL
CONSTRAINT [PK__B__0000000000000B7A] 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]

The mapping:

For Class A:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="A,AssemblyName"
table="A" lazy="true">
<id name="Id" column="Id" type="string">
<generator class="assigned"/>
</id>
<one-to-one name="_B" cascade="all" fetch="join" foreign-key="None" constrained="true"
class="B"/>
</class>
</hibernate-mapping>

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="B,AssemblyName"
table="B" lazy="true">
<id name="Id" column="Id" type="string">
<generator class="assigned"/>
</id>
<property name="_Name" column="Name"/>
</class>
</hibernate-mapping>