Generic DAO with NHibernate

http://geekswithblogs.net/Billy/archive/2006/02/15/69607.aspx

Hibernate.org has a great article on creating a generic DAO for Hibernate in Java. Below is what I use for the C# port.
 
The interface for common CRUD functionality...
 
public interface GenericDAO {
 T GetById(IdDataType id, bool shouldLock);
 List GetAll();
 List GetByExample(T exampleInstance, string[] propertiesToExclude);
 T SaveOrUpdate(T entity);
 void Delete(T entity);
}
 
The generic DAO implementation...
 
public abstract class GenericNHibernateDAO : GenericDAO
{
 /// Could be set using contruction injection IoC
 
 public GenericNHibernateDAO(ISessionManager sessionManager) {
 this.sessionManager = sessionManager;
 }
 
 
 public T GetById(IdDataType id, bool shouldLock) {
 ISession session = GetSession();
 T entity;
 
 if (shouldLock) {
 entity = (T) session.Load(persitentType, id, LockMode.Upgrade);
 }
 else {
 entity = (T) session.Load(persitentType, id);
 }
 
 return entity;
 }
 
 public List GetAll() {
 return GetByCriteria();
 }
 
 protected List GetByCriteria(params ICriterion[] criterion) {
 ISession session = GetSession();
 ICriteria criteria = session.CreateCriteria(persitentType);
 
 foreach (ICriterion criterium in criterion) {
 criteria.Add(criterium);
 }
 
 GenericUtils genericUtils = new GenericUtils();
 return genericUtils.ConvertToGenericList(criteria.List());
 }
 
 public List GetByExample(T exampleInstance, string[] propertiesToExclude) {
 ISession session = GetSession();
 ICriteria criteria = session.CreateCriteria(persitentType);
 Example example = Example.Create(exampleInstance);
 
 foreach (string propertyToExclude in propertiesToExclude) {
 example.ExcludeProperty(propertyToExclude);
 }
 
 criteria.Add(example);
 
 GenericUtils genericUtils = new GenericUtils();
 return genericUtils.ConvertToGenericList(criteria.List());
 }
 
 public T SaveOrUpdate(T entity) {
 ISession session = GetSession();
 session.SaveOrUpdate(entity);
 
 return entity;
 }
 
 public void Delete(T entity) {
 ISession session = GetSession();
 session.Delete(entity);
 }
 
 private ISession GetSession() {
 Check.Require(sessionManager != null, "sessionManager was not set");
 return sessionManager.OpenSession();
 }
 
 private Type persitentType = typeof(T);
 private ISessionManager sessionManager;
}
 
And for using this within your code...
 
public class ProjectDAONHibernate : GenericNHibernateDAO<Project, int> {
 public ProjectDAONHibernate(ISessionManager sessionManager) : base(sessionManager) {}
}