Codefirst and migrations

Question

When an application is Live an iterative approach to database changes is obviously required. In the db first world I would change the object (eg. column added to table) in the databaae project, then deploy (recreate) to my local instance, then replace the old table with the new in my edmx - when it was go Live time a delta script is generated out of the database project compared to a copy of the Live database schema. Sounds long winded but at the end of the day I only made the change once (the object in the db project) - everything else is generated

Flip over to code first (EF6) and Im expecting a similar one change experience - i.e. I add the property to the class - however do I additionally need to add a migration script ?

I've been reading and it seems many advise to disable migrations to have more control - I'm confused - I had visions of simply deploying the app and the changes automatically reflected in the target database the next time the app runs - one thing is for sure I don't want to manually write separate deployment scripts (or migration code). As mentioned I'm confused about this final part - can anyone clarify - point out the options

Many thanks

Answer 1

Short answer is there's no need to create a 'migration script', you're correct as EF will handle it for you if you want. I think when you read about disabling migrations, you were probably actually reading 'disable automatic migrations'; EF will still generate migrations regardless.

As you pointed out it IS a two-change process when developing: First you change your class, then you open up the Package Manager console and call Add-Migration. Usually, that's all you have to do, and EF will generate the change code for you. Then, you call Update-Database and it does it's work. When you go to deploy, you will connect to your target database and call Update-Database once and it will apply all migrations that are pending.

You can also enable auto-migrations which skips the Add-Migration step, but I always like to review the generated code. Call me old-fashioned ;)

It gets more complicated when you need support for views, SPROCS, and UDFs, but there are ways to do most anything you want to do. And, even though it's a 2 (3?) step process to get changes out to the DB, it's still much easier than changing the DB and code separately, by yourself.

Then, you can follow the steps here to set your deployment up so that once your EF is initialized on a connection to your production DB, it automatically applies the updates. Again, I would advise to do it yourself (via the package manager console) just to be safe but it's not necessary.