EF comes with an object-relational designer (accessible in VS) that enables you to create an object
model that is accessible through code based on the tables in your database. By adding tables to this
designer, VS generates code for you that enables you to access the underlying data in the database without
writing a lot of code. The classes that are added to the designer are stored in the .edmx fi le and its
Code Behind fi les. The designer fi le (the Code Behind of the PlanetWrox.edmx fi le) contains a class
that inherits from ObjectContext, the main object in EF that provides access to your database. In the
preceding exercise, this class is called PlanetWroxEntities (named after the .edmx fi le) and you use it
to access the data in the tables you added to the diagram. Although you normally don’t need to look at
the generated code, you can open the fi le PlanetWrox.designer.vb or PlanetWrox.designer.cs fi le
and see what code has been generated for you. The *.tt fi les you deleted enable you to customize the
code that is generated based on the underlying data model. However, in most cases you don’t have to
do this, and you can rely on the default code generation instead. That’s why you deleted these fi les, and
confi gured the EF model to use its default code generation strategy.