Is the properties in Entity must be virtual when using FluentNhibernate? - fluent-nhibernate

Question

Which entity FluentNHibernate uses as entity
I create some entity in Domain(or BLL), such as the following:
public class Role
{
public long ID { get; protected set; }
public string Name { get; set; }
public string Description { get; set; }
public List<User> Users { get; set; }
public Role()
{
Users = new List<User>();
}
}
And I want make use of FlunetNHibernate to map them, but get errors:
The following types may not be used as proxies:
Freeflying.Domain.Core.Profile: method get_ID should be 'public/protected virtual' or 'protected internal virtual'
Yes, I recall the programmer requirement when use FluentNHibernate, the entity should be like this:
public class Role
{
public virtual long ID { get; protected set; }
public virtual string Name { get; set; }
public virtual string Description { get; set; }
}
But It looks wired. Do you think so? How do you do when using FluentNHibernate? I don't want go back to Domain layer and add virtual for every property.

Answer 1

This is a basic requirement for using NHibernate; It allows NHibernate to generate a proxy class that descends from your class for lazy loading and such.
I have not seen a method of removing this requirement, though if such a thing is possible it would mean that you could not use lazy loading of objects and/or properties.
Here's a blog post that explains this a bit more; It also offers a way to avoid marking your properties as virtual, although I would really recommend that you do not use this method (marking classes to avoid lazy loading) as the benefits of lazy loading in most circumstances far outweigh the cost of making your properties virtual.