Entity Framework code-first: migration fails with update-database, forces unneccessary(?) add-migration

I also tried deleting the database again, called update-database and then add-migration. I ended up with an additional migration that seems not to change anything (see below)

Based on above details, I think you have done last thing first. If you run Update database before Add-migration, it won't update the database with your migration schemas. First you need to add the migration and then run update command.

Try them in this order using package manager console.

PM> Enable-migrations //You don't need this as you have already done it
PM> Add-migration Give_it_a_name
PM> Update-database

Entity Framework does have some issues around identity fields.

You can't add GUID identity on existing table

Migrations: does not detect changes to DatabaseGeneratedOption

Reverse engineering does not mark GUID keys with default NEWSEQUENTIALID() as store generated identities

None of these describes your issue exactly and the Down() method in your extra migration is interesting because it appears to be attempting to remove IDENTITY from the column when your CREATE TABLE in the initial migration appears to set it!

Furthermore, if you use Update-Database -Script or Update-Database -Verbose to view the sql that is run from these AlterColumn methods you will see that the sql is identical in Up and Down, and actually does nothing. IDENTITY remains unchanged (for the current version - EF 6.0.2 and below) - as described in the first 2 issues I linked to.

I think you should delete the redundant code in your extra migration and live with an empty migration for now. And you could subscribe to/vote for the issues to be addressed.

References:

Change IDENTITY option does diddly squat

Switch Identity On/Off With A Custom Migration Operation

Try this:

PM> Enable-migrations -force
PM> Add-migration MigrationName
PM> Update-database -force