NHibernate-ISession.Query< T>()所在的位置

当我尝试编译以下代码时

When I try to compile the following code

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Linq;
using NHibernate;

namespace NewNHTest
{
    class A
    { }

    class Program
    {
        static void Main(string[] args)
        {
            ISession session;
            var q = session.Query<A>();
        }
    }
}

我收到以下错误:

'NHibernate.ISession' does not contain a definition for 'Query' and no extension method 'Query' accepting a first argument of type 'NHibernate.ISession' could be found (are you missing a using directive or an assembly reference?)

NHibernate.dll版本是3.0.0.4000.
该项目的.Net版本是3.5.

NHibernate.dll version is 3.0.0.4000.
The .Net version of project is 3.5.

我做错了什么?
谢谢您的帮助！

What am I doing wrong?
Thank you for your help!