How can I use Expression<T> in NHibernate?

using System;
using System.Collections;
using System.Linq;
using System.Linq.Expressions;


public interface IRepository<T>
{
     IQueryable<T> GetAll();
     PagedList<T> GetPaged(int pageIndex, int pageSize);
     IQueryable<T> Find(Expression<Func<T, bool>> expression);
     void Save(T item);
     void Delete(T item);
}