Inheritance confusion

Hi there,
I am relatively new to developing with Lightspeed v4 and need some guidance with the best way to implement a solution to my problem. My Lightspeed model is connected to a legacy sql database, and I have an entity 'Fact' which represents the main fact table.

I would like to create a class that inherits directly from the Fact entity and implements some business logic around creating, updating and deleting records from the Fact table. I have read the blogs on this site concerning table inheritance, but since the descendent class will not add any further properties (table fields), it would seem that table inheritance does not apply ?? I intend to use a static method to retrieve the object, but am getting an error "Descendent type is not discriminated".

Here is a code sample.

public class MyBusinessObject : Fact
{
public static MyBusinessObject Load(MyUnitOfWork uow, string id)
{
Fact f = (from uow.Facts where f.Id.Equals(id) select f).First();
if (f == null) { return null; }
return (MyBusinessObject)f;
}
}

The "Descendent type is not discriminated" exception is thrown on the first line of the static Load() method. Can someone please point me in the right direction?

Thanks in advance,
Damien.

Hi Damien,

You need to apply a DiscriminatorAttribute to the derived class specifying the discriminator property name and the value for that property which can uniquely identify instances of that class when being materialised.

e.g. If you had a FactType property and all MyBusinessObjects were FactType = 1 then when declaring your DiscriminatorAttribute your property name would be FactType and the value would be 1

Jeremy

Hi Jeremy,
Thanks for your prompt reply. Does that mean that I need to add a column to the existing Fact table in sql called FactType ? or can it simply be a member of the descendent class ? I do not have authorization to change the schema of the Fact table.

Thanks again,
Damien.

You will need a column you can use to distinguish the derived entities, if you already have a way of doing this you can just wire up the DiscriminatorAttribute accordingly otherwise you will need to add a new column for this purpose.

Jeremy