private IList ListByExample(object sample)
{
   ISession session = _factory.OpenSession();
   ICriteria criteria = session.CreateCriteria(sample.GetType());

   Example ex = Example.Create(sample);
   ex.ExcludeNulls();
   ex.ExcludeZeroes();
   criteria.Add(ex);               

   return criteria.List();
}

SELECT ... FROM ... WHERE (this.CLI_DATAMAIORFATURA = '0001-01-01 00:00:00' and this.ATI_ID = '3' and this.CLI_DATAPRIMEIRACOMPRA = '0001-01-01 00:00:00' and ...)

private IList ListByExample(object sample)
{
   ISession session = _factory.OpenSession();
   ICriteria criteria = session.CreateCriteria(sample.GetType());

   Example ex = Example.Create(sample);
   ex.ExcludeNulls();
   ex.ExcludeZeroes();

   foreach (PropertyInfo info in (sample.GetType()).GetProperties())
   {
         if (info.PropertyType == typeof(DateTime))
         {
                DateTime dt = (DateTime) info.GetValue(sample, info.GetIndexParameters());
                if (dt <= DateTime.MinValue)
                    e.ExcludeProperty(info.Name);
         }
   }

   criteria.Add(ex);               

   return criteria.List();
}