There are a couple of ways we can “re-sync” our model
objects and our database:
We can manually update our database schema to match our
We can manually delete our database file, re-run the
application, and have EF automatically re-create the database
We can enable a feature of EF code-first that automatically
updates our database for us whenever we change our models
Let’s look at how we can use this last automatic option with
our NerdDinner application.
The RecreateDatabaseIfModelChanges Feature
CTP 4 of the EF Code First library includes a useful
development-time feature that enables you to automatically re-create your
database anytime you make modifications to your model classes. When you
enable it, EF identifies when any of the model classes that were used to
automatically create a database are modified, and when that happens can
re-create your database to match the new model class shape – without you having
to take any manual steps to do so.
This capability is especially useful when you are first
developing an application, since it gives you the freedom and flexibility to
quickly refactor and restructure your model code however you want - without
having to do any manual work to keep your database schema in sync along the
way. It works especially well with SQL CE – since it is a file-based
database that can be dropped and recreated on the fly in under a second.
This can enable an incredibly fluid development workflow.
The easiest way to enable this capability is to add a
Database.SetInitializer() call to the Application_Start() event handler within
our Global.asax class:
This tells EF to re-create our NerdDinners.sdf
database to match our NerdDinners model anytime our model classes change
shape. Now when we re-run our application we will no longer get that
error message telling us that our model classes and database are out of
sync. EF will instead automatically re-create a database for us that
matches our new model class shape, and our application will run fine: