Mapping entity oneToMany with fluent nhibernate

Question

The problem appears to be simple however I\'m having so much trouble trying to map this entities. I just can\'t see what am I doing wrong. Can you guys help me?

I have th

Answer 1

After all, with these SQL scripts (adjust for SQL Server in my case)

CREATE TABLE CLIENTE
(
  CORE_ID                      int           NOT NULL,
  CORE_NUMERO_MEDIDOR          VARCHAR(50)
)

CREATE TABLE MEDIDOR
(
  NUMERO_MEDIDOR  VARCHAR(50),
  MARCA_MEDIDOR   VARCHAR(50)
)

With these entities (all properties are virtual)

public class Cliente
{    
    public virtual int ClienteId { get; set; }  
    public virtual IList<Medidor> ListaMedidores { get; set; }   
    public virtual string NumeroMedidor { get; set; }       
}
public class Medidor
{
    public virtual string NumeroMedidor { get; set; }
    public virtual string MarcaMedidor { get; set; }
    public virtual Cliente Cliente { get; set; }
}

and with only this one mapping in place:

public class ClienteMap: ClassMap<Cliente>
{
    public ClienteMap()
    {
        Table("CLIENTE");
        Id(x => x.ClienteId, "CORE_ID");
        Map(x => x.NumeroMedidor).Column("CORE_NUMERO_MEDIDOR");
        HasMany(x => x.ListaMedidores)
            .KeyColumn("NUMERO_MEDIDOR")
            .Component(com =>
            {
                com.ParentReference(y => y.Cliente);
                com.Map(y => y.MarcaMedidor, "MARCA_MEDIDOR");
            })
            .PropertyRef("NumeroMedidor")
            .Table("MEDIDOR")
            // .Inverse() // NO INVERSE, won't work
            .Cascade.All();
    }
}

I can confirm, that this query will work:

var list = session.Query<Cliente>().Fetch(x => x.ListaMedidores).ToList();
var firt = list.First().ListaMedidores.First();
var last = list.First().ListaMedidores.Last();
Assert.IsTrue(firt.MarcaMedidor != last.MarcaMedidor);

BTW, this will be (my preferred) generated xml mapping:

<class xmlns="urn:nhibernate-mapping-2.2" name="Cliente" table="CLIENTE">
    <id name="ClienteId" type="System.Int32">
      <column name="CORE_ID" />
      <generator class="identity" />
    </id>
    <bag cascade="all" name="ListaMedidores" table="MEDIDOR">
      <key property-ref="NumeroMedidor">
        <column name="NUMERO_MEDIDOR" />
      </key>
      <composite-element class="Medidor">
        <parent name="Cliente" />
        <property name="MarcaMedidor" type="System.String">
          <column name="MARCA_MEDIDOR" />
        </property>
      </composite-element>
    </bag>
    <property name="NumeroMedidor" type="System.String">
      <column name="CORE_NUMERO_MEDIDOR" />
    </property>
</class>

For documentation see:

7.2. Collections of dependent objects

Answer 2

The one-to-many and many-to-one are always related by one column. This is such column, which contains reference ID (foreign key) to the other table / entity.

In our case, it must be column in table of Medidor, and its name would be "CORE_NUMERO_MEDIDOR". The mapping should look like this

public ClienteMap()
{
    ...
    HasMany(x => x.ListaMedidores)
       //.KeyColumn("NUMERO_MEDIDOR")
       .KeyColumn("CORE_NUMERO_MEDIDOR") // column in other table
       .Inverse().Cascade.All();
}


public MedidorMap()
{
    ...
    References(x => x.Cliente)
        .Column("CORE_NUMERO_MEDIDOR");  // column in this table
}

EXTEND

Based on extended question, when we can see this structure of tables

CREATE TABLE CLIENTE
(
  CORE_ID                      NUMBER           NOT NULL,
  CORE_NUMERO_MEDIDOR          VARCHAR2(50 BYTE)
)

CREATE TABLE MEDIDOR
(
  NUMERO_MEDIDOR  VARCHAR2(50 BYTE),
  MARCA_MEDIDOR   VARCHAR2(50 BYTE)
)

That the DB reference is different then in C#. It seems, like if

table CLIENTE references just one MEDIDOR, while MEDIDOR has many CLIENTEs.

It seems that the objects should look like this:

public class Cliente
{    
    ...
    //public IList<Medidor> ListaMedidores { get; set; }    
    //public Medidor Medidor { get; set; }    
}

public class Medidor
{
    ...
    //public virtual Cliente Cliente { get; set; }
    public virtual IList<Cliente> Clientes { get; set; }
}

and the mapping should be

public ClienteMap()
{
    ...
    References(x => x.Medidor, "CORE_NUMERO_MEDIDOR");
}


public MedidorMap()
{
    ...
    Id(x => x.NumeroMedidor).Column("NUMERO_MEDIDOR")
                               // column in this table to be compared
    HasMany(x => x.Clientes)
       .KeyColumn("CORE_NUMERO_MEDIDOR") // with column in other table
       .Inverse().Cascade.All();
}

ANOTHER EXTEND

Because the second table MEDIDOR is not having its own primary key (column NUMERO_MEDIDOR) but it could contain many same values... coming from CLIENT TABLE... we should use component mapping

public ClienteMap()
{
    ...
    Map(x => x.NumeroMedidor).Column("CORE_NUMERO_MEDIDOR");
    HasMany(x => x.ListaMedidores)
        .Component(com =>
        {
            com.Parent(y => y.Cliente, "NUMERO_MEDIDOR")
               .PropertyRef("NumeroMedidor")
               ;
            com.Map(y => y.MarcaMedidor, "MARCA_MEDIDOR");
        })
        .PropertyRef("NumeroMedidor")
        .Table("MEDIDOR")
       // .Inverse() // NO INVERSE, won't work
       .Cascade.All();

}