FluentNHibernate subclass and hierarchical data - fluent-nhibernate

Question

I have an Account table that stores Master Accounts and Sub Accounts. Master Accounts are basically the same as Sub Accounts except that they can have an associated Company. Account is an abstract class and both MasterAccount and SubAccount derive from it.
A MasterAccount is any account entry with a null ParentAccountId. If an Account record has a ParentAccountId then it is a SubAccount and the ParentAccountId references the AccountId field for the MasterAccount.
I am trying get FluentNhibernate mappings for them.
The classes look like the following
public class Account : EntityBase
{
public Account() { }
public virtual string AccountNumber { get; set; }
public virtual string AccountName { get; set; }
public virtual string ContactRole { get; set; }
public virtual bool EmailBillDataFile { get; set; }
public virtual bool EmailBill { get; set; }
public virtual bool PostBill { get; set; }
public virtual BillingMethod BillingMethod { get; set; }
public virtual BillingAddressType BillingAddressType { get; set; }
public virtual Contact Contact { get; set; }
public virtual bool IsInvoiceRoot { get; set; }
public virtual string Password { get; set; }
public virtual bool HasRequestedInvoicing { get; set; }
public virtual bool IsInternational { get; set; }
public virtual decimal AmountPaid { get; set; }
public virtual decimal PreviousBill { get; set; }
public virtual void MakePayment(decimal amount)
{
MakePayment(amount, null);
}
public virtual void MakePayment(decimal amount, string invoiceNumber)
{
AmountPaid += amount;
if (string.IsNullOrEmpty(invoiceNumber))
LogActivity(string.Format("Made payment of {0:c}", amount));
else {
LogActivity(string.Format("Made payment of {0:c} on Invoice '{1}'", amount, invoiceNumber));
}
}
public virtual Invoice CreateInvoice()
{
Invoice invoice;
invoice = IsInternational ? new NoGstInvoice() : new Invoice();
// Can update invoice properties that rely on account data here.
return invoice;
}
#region Business Rules
public override IEnumerable<RuleViolation> GetRuleViolations()
{
if (string.IsNullOrEmpty(AccountName))
yield return new RuleViolation("Account Name required", "AccountName");
if (string.IsNullOrEmpty(AccountNumber))
yield return new RuleViolation("Acocunt Number required", "AccountNumber");
if (string.IsNullOrEmpty(Password))
yield return new RuleViolation("Password required", "Password");
yield break;
}
#endregion
}
public class MasterAccount : Account
{
private Company _company;
private IList<SubAccount> _subAccounts;
public MasterAccount() : this(null) { }
public MasterAccount(Company company)
{
_company = company;
_subAccounts = new List<SubAccount>();
}
public virtual Company Company
{
get { return _company; }
}
public virtual IEnumerable<SubAccount> SubAccounts
{
get { return _subAccounts; }
}
public virtual SubAccount CreateSubAccount(string accountNumber, string accountName)
{
var subAccount = new SubAccount(this)
{
AccountName = accountName,
AccountNumber = accountNumber,
Contact = this.Contact,
ContactRole = this.ContactRole,
PreviousBill = 0,
AmountPaid = 0,
BillingAddressType = this.BillingAddressType,
BillingMethod = this.BillingMethod,
IsInternational = this.IsInternational,
IsInvoiceRoot = false,
EmailBill = this.EmailBill,
EmailBillDataFile = this.EmailBillDataFile,
Password = this.Password,
PostBill = this.PostBill
};
return subAccount;
}
}
public class SubAccount : Account
{
private MasterAccount _masterAccount;
public SubAccount() { }
public SubAccount(MasterAccount master)
{
_masterAccount = master;
}
public virtual MasterAccount MasterAccount
{
get { return _masterAccount; }
}
}
The mappings I have are:
public class AccountMap : ClassMap<Account>
{
public AccountMap()
{
Table("Account");
Id(x => x.Id).Column("AccountId").GeneratedBy.Identity();
Map(x => x.AccountName).Length(50).Not.Nullable();
Map(x => x.AccountNumber).Length(10).Not.Nullable();
Map(x => x.ContactRole).Length(50);
Map(x => x.BillingMethod).Not.Nullable();
Map(x => x.EmailBill).Not.Nullable();
Map(x => x.PostBill).Not.Nullable();
Map(x => x.EmailBillDataFile).Not.Nullable();
Map(x => x.BillingAddressType).Not.Nullable();
Map(x => x.IsInvoiceRoot).Not.Nullable();
Map(x => x.HasRequestedInvoicing).Not.Nullable();
Map(x => x.IsInternational).Not.Nullable();
Map(x => x.PreviousBill).Not.Nullable();
Map(x => x.AmountPaid).Not.Nullable();
Map(x => x.Password).Length(20).Not.Nullable();
References(x => x.Contact).Column("ContactId").Not.Nullable();
DiscriminateSubClassesOnColumn("ParentAccountId");
}
}
public class MasterAccountMap : SubclassMap<MasterAccount>
{
public MasterAccountMap()
{
References(x => x.Company).Column("CompanyId");
HasMany(x => x.SubAccounts).KeyColumn("ParentAccountId").Inverse().Cascade.All();
}
}
public class SubAccountMap : SubclassMap<SubAccount>
{
public SubAccountMap()
{
References(x => x.MasterAccount).Column("ParentAccountId").Not.Nullable();
}
}
However, when I execute the following test:
[Test]
public void Can_add_subAccount_to_database()
{
var master = Session.Get<MasterAccount>(1);
var subAccount = master.CreateSubAccount("TST123", "Test Account");
Session.Save(subAccount);
Session.Flush();
Session.Clear();
var fromDb = Session.Get<SubAccount>(subAccount.Id);
Assert.AreNotSame(subAccount, fromDb);
}
I get an exception on the Session.Save(subAccount); line.
System.ArgumentOutOfRangeException : Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
I do not get the exception if I comment out the References mapping in SubAccountMap.
Any help on correctly mapping this relationship is appreciated.

Answer 1

Seems I needed to use the Formula method off DiscriminateSubClassesOnColumn
DiscriminateSubClassesOnColumn("").Formula("case when parentaccountid is null then '0' else '1' end");
and then use the following in each of the subclasses
DiscriminatorValue("0"); // In MasterAccountMap
DiscriminatorValue("1"); // in SubAccountMap
see http://wiki.fluentnhibernate.org/Fluent_mapping