/// <summary>
/// Given a collection of entity instances that used to
/// belong to the collection, and a collection of instances
/// that currently belong, return a collection of orphans
/// </summary>
protected virtual ICollection GetOrphans(ICollection oldElements, ICollection currentElements, string entityName, ISessionImplementor session)
{
// short-circuit(s)
if (currentElements.Count == 0)
{
// no new elements, the old list contains only Orphans
return(oldElements);
}
if (oldElements.Count == 0)
{
// no old elements, so no Orphans neither
return(oldElements);
}
if (currentElements.Count == oldElements.Count && currentElements.Cast <object>().SequenceEqual(oldElements.Cast <object>(), new IdentityEqualityComparer()))
{
return(Array.Empty <object>());
}
var persister = session.Factory.GetEntityPersister(entityName);
IType idType = persister.IdentifierType;
var currentObjects = new HashSet <object>(new TypeComparer(idType, session.Factory));
foreach (object current in currentElements)
{
if (current != null)
{
var id = ForeignKeys.GetIdentifier(persister, current);
if (id != null)
{
currentObjects.Add(id);
}
}
}
List <object> res = new List <object>();
// oldElements may contain new elements (one case when session.Save is called on new object with collection filled with new objects)
foreach (object old in oldElements)
{
if (old != null)
{
var id = ForeignKeys.GetIdentifier(persister, old);
if (id != null)
{
if (!currentObjects.Contains(id))
{
res.Add(old);
}
}
}
}
return(res);
}