问题
I have an asp.net core mvc website using entity framework core.
I don't know how it initially happened, but I can't get past the error: "There is already an object named AspNetRoles in the database"
I ended up deleted the database, deleting all my migration .cs files and starting from scratch.
I've then tried
add-migration MyInitialMigration
same error
I then deleted the database again, and tried a direct
update-database
(without adding a migration)
still the same error
I tried changing the appsettings config string to point to a new, non-existing database.
Still the same error!
Previously on MVC5/EF6 I've encountered this error and have resolved it using the same method as this answer: There is already an object named in the database
-Add-Migration Initial -IgnoreChanges
However -IgnoreChanges is unsupported in EFCore
Or previously on EF6 I've resolved it by adding a migration, then deleting everything in the Up/Down and running an empty migration. This has not worked on EFCore
How can I continue? I've checked the migration table and they're always empty even though it's created the whole database each time. Just doesn't seemed to have logged it in the migrations table
回答1:
Found my issue.
I had followed this tutorial to load appsettings from EntityFramework: https://docs.asp.net/en/latest/fundamentals/configuration.html#example-entity-framework-settings
In the EntityFrameworkConfigurationProvider there is a public override void Load() which has a dbContext.Database.EnsureCreated(); and a CreateAndSaveDefaultValues
Between the two of those it looks like it was initializing the database without tracking the migration.
I commented those out, ran a migration and it worked fine. Hopefully I don't have to comment them out every time I want to run a migration :/
回答2:
I've just had the same issue, and seems like Database.EnsureCreated() doesn't use migrations, you can use Database.Migrate() instead which is what I've just tried and seems to work, but time will tell when I try another migration.
来源：https://stackoverflow.com/questions/39609551/there-is-already-an-object-named-aspnetroles-in-the-database-entity-framework