Ibatis的lazyload失效怎么办？

以前使用DataMapper-1.6.1，现在改用DataMapper-1.5.1，结果lazyload无效了。
以下引用《Data Mapper Guide-1.6.1.chm》中的内容：

Use the lazyLoad attribute with the select attribute to indicate whether or
not the select statement's results should be lazy loaded. This can provide a
performance boost by delaying the loading of the select statement's results
until they are needed/accessed.

Lazy loading is supported transparently for IList and IList<T>
implementation.

Lazy loading is supported on strongly typed collection via
Castle.DynamicProxy component. In this case you must set the listClass attribute
and declare all methods/properties of the typed collection that you want to
proxy as virtual.

Lazy loading is supported on concrete class via Castle.DynamicProxy
component. In this case, you must declare all methods/properties of the class
that you want to proxy as virtual.

在1.5.1版本中，我没有把lazyload属性定义为virtual都可以使用lazyload功能，现在即使声明为virtual也没有效果。调试的过程中发现，属性的第一次读取是肯定为空的，而之后lazyload属性的值却有可能获取。深入分析代码并把1.6.1和1.5.1做比较，无奈水平有限，发现直接相关的代码似乎没有改动，没看出端倪。

在Ibatis.Net的Issue Tracker上看到了此bug的报告，但是没有评论和解决方案。不知道cnblogs上研究Ibatis.Net的牛人能不能提供帮助？实在不行，只有使用1.5.1了。

附代码：