NHibernate使用手迹(2nd—extension)

在做顾客银行这个例子的时候，怎么也进行不下去了，遇到了如下一个错误：Object type cannot be converted to target type.

我想做的事情是这样的：我把需求稍微改动了一下，Customer和Bank不再是one-to-one了，而是one-to-many.
那么我在配置文件中改成：

Customer.hbm.xml

<bag name="CustomerBanks"

             cascade="all"

             order-by="BankName asc">

             <key column="CustomerID" />

             <one-to-many class="Data.Bank, Data"/>

        </bag>

 

Bank.hbm.xml

<many-to-one name="BankCustomer" class="Data.Customer, Data"

                     cascade="all" outer-join="auto"                  

                     column="CustomerID"

                     not-null="false" />

详细的配置文件、Domain Model 和 DB Model在此下载！
然后我想插入Customer的时候同时插入Bank，实现代码如下
           Customer aCustomer = new Customer();

           aCustomer.CustomerTitle = "Developer";

           aCustomer.CustomerAge = 25;

           aCustomer.UpdateTimestamp = DateTime.Now;

 

           Bank aBank = new Bank();

          

           aBank.BankName = "CICB";

           aBank.Banlance = 1233453.234M;

           aBank.UpdateTimestamp = aCustomer.UpdateTimestamp;

 

           // bind the two object to each other.

           aBank.BankCustomer = aCustomer;

           aCustomer.CustomerBanks.Add(aBank);

 

           aEntityRule.Save(aCustomer);

为什么出现错误，Object type cannot be converted to target type.

我用SQL Profile察看，发现根本没有生成任何SQL 语句，请指点一下哪里错了