Question

I have tried many different mapping configurations but continue to generate exceptions or create / update the wrong record.

Exceptions

• Cannot insert explicit value for identity column in table
• Cannot use identity column key generation with union-subclass mapping
• null id generated for class XXX

When I have a map that does save I have the following problem

I have successfully inserted and updated records in the database but these records do not have the appropriate id. They all have 0 for an id and as such only update the same record over and over.

Problem I am trying to solve

I am attempting to SubclassMap the interface IRequest. This interface is used as a property on a separate class AbstractWorkflowRequestInformation. When saving the parent class I want to save the referenced IRequest in the appropriate sub-class table. This is my current mapping which generates the exception Cannot insert explicit value for identity column in table. I am sure I have something tweaked in the way I am mapping the relationship between these two classes. What am I doing wrong? My maps are below.

IRequestMap

public class IRequestMap : ClassMap<IRequest>
{
    public IRequestMap()
    {
        Id(x => x.WorkflowRequestInformation)
            .GeneratedBy.Foreign("AbstractWorkflowRequestInformation");
        UseUnionSubclassForInheritanceMapping();
    }
}

public class PlanRequestMap : SubclassMap<PlanRequest>
{
    public PlanRequestMap()
    {
        Table("plan_request");
        // specific to PlanRequest property mappings and references
    }
}

public class BnjRequestMap : SubclassMap<BnjRequest>
{
    public BnjRequestMap()
    {
        Table("scratchdb.guest.bnj_request");
        // specific to BnjRequest property mappings and references
    }
}

AbstractWorkflowRequestInformationMap

public class AbstractWorkflowRequestInformationMap :
    ClassMap<AbstractWorkflowRequestInformation>
{
    public AbstractWorkflowRequestInformationMap()
    {
        Table("workflow_request_information");
        Id(x => x.Id)
            .Column("workflow_request_information_id")
            .GeneratedBy.Identity();

        // more property mappings and references
        References(x => x.SuperDuperRequest, "workflow_request_information_id")
            .Class<IRequest>().Unique().Cascade.All();
        // more property mappings and references
    }
}

Answer 1

The issue here was that my IRequest map was missing a constraining reference back to AbstractWorkflowRequestInformation. So by adding a WorkflowRequestInformation property and the constraint everything now works as I intended.

public class IRequestMap : ClassMap<IRequest>
{
    public IRequestMap()
    {
        // adding this fixed the problem
        HasOne(x => x.WorkflowRequestInformation).Constrained();
        // adding this fixed the problem

        Id(x => x.WorkflowRequestInformation)
            .GeneratedBy.Foreign("AbstractWorkflowRequestInformation");
        UseUnionSubclassForInheritanceMapping();
    }
}