FluentNhibernate mapping and struct

Question

I tought that it's simple problem, just few minuts in gogle and I got the solution etc. But, actually, I found nothing special.

So I got a struct(or class whatever) and a class where every field got such struct type. And I want to make/use table in my database using model, where each field got such type as struct.

As example struct is here

public class myStruct
{
    public float value;
    public string description;
}

and here the model which I want to use

public class FieldSummaryRow
{
    public int Id{ get; set } 
    public myStruct A { get; set; }
    public myStruct B { get; set; }
    public myStruct C { get; set; }
    public class FieldSummaryMap: ClassMap<FieldSummaryRow>
    {
      public FieldSummaryMap()
      {
        Id(x => x.Id);
        Map (x=>x.A);
        Map (x=>x.B);
        Map (x=>x.C);
      }
    }
}

But as I assume it just wouldn't work like that because of myStruct is not mapped correctly. So how should I solve this problem? Or do I nned map myStruct the same way before?

Answer 1

From NHibernate perspective, we should think about your struct as a <component>. It means, that there must be columns valueA and descriptionA for myStruct A, the same for B and C.

See the documentation:

• 5.1.13. component, dynamic-component
• Ayende's component mapping

Such a <component> myStruct would be at the end mapped like this xml snippet:

<class name="FieldSummaryRow" table="...>
    ....

    <component class="myStruct" name="A">
      <property name="value"       column="valueA"       access="field" />
      <property name="description" column="descriptionA" access="field" />
    </component>

    <component class="myStruct" name="B">
    ...

</class>

As we can see here (article by Adam Bar - see the second half as a great summary of Fluent mapping)

• Mapping-by-Code - Component (and odd cases of Fluent NHibernate's fluency)

we would need this:

public class FieldSummaryMap: ClassMap<FieldSummaryRow>
{
    public FieldSummaryMap()
    {
        Id(x => x.Id);
        Component(x => x.A, c =>
        {        
            c.Map(x => x.value).Column("valueA").Access.CamelCaseField();
            c.Map(x => x.description).Column("descriptionA").Access.CamelCaseField();
        }
        Component(x => x.B, c =>
        ...
    }
}