ADO.NET实体数据模型允许循环外键引用

I am using the new ADO.NET Entity Data Model on a simple database. I have a table/entity with a primary key (PageID) and a ParentID foreign key that references back to itself on PageID for a parent/child "0..1 to many" relationship. On a ASP.Net page, I'm using a FormView with a asp:DynamicControl to express this as a control. That part works fine except for one crucial detail: When the page renders, the list of possible parents includes itself, and setting an item to have a parent of itself causes no errors and saves to the database. Obviously a hierarchical object isn't supposed to have a parent of itself, so how do I restrict this behavior?I am using the new ADO.NET Entity Data Model on