NHibernate child deletion problem.

Question

Suppose, I have saved some permissions in the database by using this code:

RoleRepository roleRep = new RoleRepository();
Role role = new Role();
role.PermissionItems = Permission.GetList();
roleRep .SaveOrUpdate(role);

Now, I need this code to delete the PermissionItem(s) associated with a Role when role.PermissionItems == null.

Here is the code:

RoleRepository roleRep = new RoleRepository();
Role role = roleRep.Get(roleId);
role.PermissionItems = null;
roleRep .SaveOrUpdate(role);

But this is not happening.

What should be the correct way to cope with this situation?

What/how should I change, hbm-file or persistance code?

Role.cs

public class Role
{
    public virtual string RoleName { get; set; }
    public virtual bool IsActive { get; set; }
    public virtual IList<Permission> PermissionItems { get; set; }
}

Role.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="POCO" namespace="POCO">
  <class name="Role" table="Role">
    <id name="ID" column="ID">
      <generator class="native" />
    </id>    
    <property name="RoleName" column="RoleName" />
    <property name="IsActive" column="IsActive" type="System.Boolean" />
    <bag name="PermissionItems" table="Permission" cascade="all" inverse="true">
      <key column="RoleID"/>
      <one-to-many class="Permission" />
    </bag>    
  </class>  
</hibernate-mapping>

Permission.cs

public class Permission
{
    public virtual string MenuItemKey { get; set; }
    public virtual int RoleID { get; set; }
    public virtual Role Role { get; set; }
}

Permission.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="POCO" namespace="POCO">
  <class name="Permission" table="Permission">
    <id name="ID" column="ID">
      <generator class="native"/>
    </id>
    <property name="MenuItemKey" column="MenuItemKey" />
    <property name="RoleID" column="RoleID" />
    <many-to-one name="Role" column="RoleID" not-null="true" cascade="all">      
    </many-to-one>
  </class>
</hibernate-mapping>

Repository.cs

......
    public void SaveOrUpdate(T obj)
            {
                try
                {
                    if (!_session.Transaction.IsActive)
                    {
                        _session.BeginTransaction();
                        _session.SaveOrUpdate(obj);
                        _session.Transaction.Commit();
                        _session.Flush();
                    }
                    else
                    {
                        throw new Exception(CustomErrorMessage.TransactionAlreayInProgress);
                    }
                }
                catch (Exception ex)
                {
                    _session.Transaction.Rollback();
                    _session.Clear();

                    throw ex;
                }
            }
......

RoleRepository.cs

public class RoleRepository : Repository<Role>, IRoleRepository
    {
    }

Answer 1

Change the Role mapping to cascade all-delete-orphan so that orphaned Permission records are deleted:

<bag name="PermissionItems" table="Permission" cascade="all-delete-orphan" inverse="true">

and call clear on the collection instead of setting it to null:

role.PermissionItems.Clear();

The orphaned Permission records will be deleted when the session is flushed.

PS: Your catch block in the repository should call throw; not throw ex;.