从旧项目(.net 1.1)升级到.net 4.0
实体类属性都没有virtual熟悉，运行会报错。
如果一个一个实体类修改，工作量挺大的，幸好我们有开源的 virtuosity，帮助把属性改成virtual
修改的原则：
What it actually does to your assembly
- Selects all members that meet the following criteria
- from non sealed classes
- non static members
- non abstract members
- non private members
- non virtual members
- Change them to virtual
- For all (now virtual) members
- change calls to those members to virtual
- change new modifiers to override modifiers