How to completely reset all Entity Framework 6 migration history? (Zombie migrations!)

Question

Short version:

After deleting the entire database (including __MigrationHistory) AND all the migrations in the solution... somehow, named migrations are being found somewhere and applied by DbMigrator! Where are they coming from???

Long version:

We are using Entity Framework 6, against SQL Server 2012. It's an MVC webapp, and we are using code-based migrations, and we have a moderately long history of migrations at this point. We run migrations at startup:

public class MvcApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        ...

        var configuration = new Configuration();
        var migrator = new DbMigrator(configuration);
        migrator.Update();
    }
}

On several PCs it is working fine, but on just one new PC, I have problems where it seems out of synch in some way. Whenever the app runs, it complains that there are pending changes.

System.Data.Entity.Migrations.Infrastructure.AutomaticMigrationsDisabledException occurred
HResult=-2146233088
Message=Unable to update database to match the current model because there are pending changes and automatic migration is disabled. Either write the pending model changes to a code-based migration or enable automatic migration. Set DbMigrationsConfiguration.AutomaticMigrationsEnabled to true to enable automatic migration.
Source=EntityFramework
StackTrace:
     at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
     at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Upgrade(IEnumerable`1 pendingMigrations, String targetMigrationId, String lastMigrationId)
     at System.Data.Entity.Migrations.DbMigrator.UpdateInternal(String targetMigration)
     at System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClassc.<Update>b__b()
     at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
     at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)
     at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
     at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update()
     at CVInsights.MvcApplication.Application_Start() in c:\Work\ClearVision\CVO\CVInsights\Global.asax.cs:line 20
InnerException: 

But running add-migration shows no changes, and update-database does nothing.

So, giving up for the moment, I wanted to "reset" EF migrations fully. So I deleted the entire database (obviously including the __MigrationHistory table). And I deleted all the migrations from the IDE Migrations folder.

Now... when I start our app on this new PC... the DbMigrator still finds and applies a bunch of named migrations from somewhere! It isn't the complete list we presently have (in our source control), but it is the list up to a certain point a few weeks ago. After applying some of these "zombie migrations", it throws the same old exception "

Where the heck are they coming from??

I feel like I must be doing something very stupid, or the PC is fundamentally messed up...

Configuration.cs:

public sealed class Configuration : DbMigrationsConfiguration<CloudDatabase.DAL.DatabaseContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = false;
    }

    protected override void Seed(CloudDatabase.DAL.DatabaseContext context)
    {            

        context.Roles.AddOrUpdate(role => role.ID, // This is the primary key or the table we are adding to or updating.
            new Role() { ID = 1, Name = "A role" },
            new Role() { ID = 2, Name = "another role" },
            new Role() { ID = 3, Name = "third role" }
        );
    }
}

Answer 1

Based on the comments chain and what you seem to have tried, I would suggest the following course of action. Please note I am assuming you have a code store of some form (if not please backup your code).

1. Drop the database in question.
2. Close all copies of Visual Studio.
3. Delete the source from your solution folder (all of it, leave nothing behind).
4. Extract a copy of the code from your code store (Pull, Get etc)
5. Rebuild the solution
6. Run the update-database command and run your project.

If that does not fix your project then my guess would be its a problem with the Visual Studio installation (reinstall, I hope not).

Good luck.