How set foreign key to null when entity keys are of type bigint (ulong)? - codefluent

Question

In my model I'm using bigint (ulong) as the type for entity keys. I want the database to enforce referential integrity, so I have set persistenceEnforce to true. Columns for foreign keys are nullable. With referential integrity an entity can only be deleted if no foreign key is referring to the entity, so before deleting an entity I must first set each foreign key for this associated entity to null. However, I don't know how to clear the foreign key.
Here is my model:
<cf:entity name="Order" cfom:bindingList="false">
<cf:property name="Id" typeName="ulong" key="true" persistenceIdentity="true" cfps:hint="CLUSTERED" />
<cf:property name="Invoice" typeName="Invoice" persistenceEnforce="true" />
</cf:entity>
<cf:entity name="Invoice" cfom:bindingList="false">
<cf:property name="Id" typeName="ulong" key="true" persistenceIdentity="true" cfps:hint="CLUSTERED" />
<cf:property name="Name" typeName="string" />
</cf:entity>
Here is my code:
Invoice invoice = new Invoice();
invoice.Save();
Order order = new Order();
order.Invoice = invoice;
order.Save();
// We must clear the reference to the invoice before deleting the invoice,
// because the database enforces referential integrity.
order.InvoiceId = 0;
order.Save();
invoice.Delete();
The above code throws the following exception when saving the order for the second time:
The UPDATE statement conflicted with the FOREIGN KEY constraint \"FK_Ord_Ore_Inv_Inv\".
This is because the code produced by CodeFluent inserts the value 0 instead of null into the "Order_Invoice_Id" column. The following line in the Order.BaseSave method seems to be wrong:
persistence.AddParameter("#Order_Invoice_Id", this.InvoiceId, ((ulong)(0ul)));
I tried the settings persistenceDefaultValue="null" and usePersistenceDefaultValue="true" on the Invoice propery, but that did not solve the problem.

Answer 1

Note: A property of type UInt64 (unsigned) is translated to a column of type bigint (signed). So be careful with the conversions... FYI CodeFluent Entities uses CodeFluent.Runtime.Utilities.ConvertUtilities to convert values.
The overload AddParameter(string name, ulong value, ulong defaultValue) doesn't use the default value, so it does not translate the default value to NULL. As a workaround, you can create a PersistenceHook that changes the value of the parameter to match the expected behavior:
public class CustomPersistenceHook : BasePersistenceHook
{
public override void AfterAddParameter(string name, object value, IDbDataParameter parameter)
{
if (value is ulong && name == "#Order_Invoice_Id")
{
var defaultValue = (ulong)ContextData["defaultValue"];
if (defaultValue == (ulong)value)
{
parameter.Value = DBNull.Value;
}
}
base.AfterAddParameter(name, value, parameter);
}
}
Then, you need to register the persistence hook:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="Sample" type="CodeFluent.Runtime.CodeFluentConfigurationSectionHandler, CodeFluent.Runtime" />
</configSections>
<Sample persistenceHookTypeName="Sample.CustomPersistenceHook, Sample" />
</configuration>