多个复合主键在Fluent nHibernate中作为外键映射引用

Question

这是一个遗留的表结构，因此无法进行架构修改。

Patient
-------
Code - PK
HospitalCode - PK - FK with Hospital.Code
HospitalGroup - PK - FK with Hospital.HospitalGroup
Other fields

Hospital
-------
Code - PK
HospitalGroup - PK - FK with HospitalGroup.Code
Other fields

Department
-------
Code - PK
HospitalCode - PK - FK with Hospital.Code
HospitalGroup - PK - FK with HospitalGroup.Code
Other fields

Diagnose
-------
PatientCode - PK - FK with Patient.Code
HospitalCode - PK - FK with Hospital.Code
HospitalGroup - PK - FK with Hospital.HospitalGroup
DepartmentCode - PK - FK with Department.Code
Other fields

映射如下所示

public class PatientMap : ClassMap<Patient>
{
    public PatientMap()
    {
        CompositeId()
           .KeyProperty(x => x.Id, "ID")
           .KeyReference(x => x.Hospital, "Hospital_id", "HospitalGroup_id")
           .KeyReference(x => x.HospitalGroup, "HospitalGroup_id");

        Map(x => x.Name);            
    }
}

public class HospitalMap : ClassMap<Hospital>
{
    public HospitalMap()
    {
        CompositeId()
          .KeyProperty(x => x.Id, "ID")              
          .KeyReference(x => x.HospitalGroup, "HospitalGroup_id");

        Map(x => x.Name);            
    }
}

public class HospitalGroupMap : ClassMap<HospitalGroup>
{
    public HospitalGroupMap()
    {
        Id(x => x.Id).Column("ID");            
        Map(x => x.Name);                        
    }
}    

public class DepartmentMap : ClassMap<Department>
{
    public DepartmentMap()
    {
       CompositeId()
           .KeyProperty(x => x.Id, "ID")
           .KeyReference(x => x.Hospital, "Hospital_id", "HospitalGroup_id")
           .KeyReference(x => x.HospitalGroup, "HospitalGroup_id");

        Map(x => x.Name);                      
    }
}

public class DiagnoseMap : ClassMap<Diagnose>
{
    public DiagnoseMap()
    {
        CompositeId()
            //.KeyReference(x => x.Hospital, "Hospital_id", "HospitalGroup_id")
            //.KeyReference(x => x.HospitalGroup, "HospitalGroup_id")
            .KeyReference(x => x.Department, "Department_id", "Hospital_id", "HospitalGroup_id")
            .KeyReference(x => x.Patient, "Patient_id", "Hospital_id", "HospitalGroup_id");
    }
}

如何制作流畅的地图，以便我能够获得

Patient.DiagnoseList[0].Department.Hospital.Code

目前我收到以下异常

"identifier mapping has wrong number of columns: Examples.FirstProject.Entities.Diagnose type: component[Department,Patient]"