Run entity framework code first migration on different database

Question

I am using EF code first to create my database, the application is in production and test now so I need to run migrations to update the database as my model changes.

I have set up migrations based on the standard instructions and it works fine, against dev database one. I also have a second database that I want to bring in line with the current code base but this second database is in an unknown state.

What I want to know is can I generate a migration class against a different database and how do I do that? I can't seem to generate a migration class against anything other than the original database I specified when I set up migrations. I have changed the DB name in the app.config but it still looks at the original database when doing migrations.

How can I explicitly specify which database to generate the migration script against?

Answer 1

Migrations don't look at the database other than to check if a migration has been applied (__MigrationHistory). When you setup migrations it takes a snapshot of the code models and uses that when moving forward. So if you want to bring a database in an unknown state under migration control you will need to get it to match the code model.

You could do something similar to this: Create an idempotent script from your current database (update-database -Script –SourceMigration $InitialDatabase). This will be the equivalent of all migrations needed to create and bring your database current. Since you have an existing database where some of these objects exist, you will need to manually adjust the script by removing the code for items that already exist. Once you get it to apply, you should have a database that matches your model with a populated __MigrationHistory table.

Another option is to use a schema compare utility to make the databases match and then just copy the __MigrationHistory table over.

See Migrations Under the Hood.