Seeding multiple databases with single Entity Framework context

Question

I am developing a single-instance, multi-tenant web application, with a SQL database using Entity Framework 6 Code-First. 
I want to have a separate database for each client, generated from the same EF models, with a single DbContext. The database to connect to will be determined by the subdomain that the client is using the web app from. 
This seems to work fine and the correct database is connected to depending on the subdomain. However my issue is seeding the databases with data. This is the code I have:
foreach (var connString in ConfigurationManager.ConnectionStrings.Cast<ConnectionStringSettings>()))
Configuration.PerformDatabaseMigration(connString.Name);
This then calls the PerformDatabaseMigration method: 
public class Configuration : DbMigrationsConfiguration<DataContext>
public Configuration()
AutomaticMigrationsEnabled = false;
AutomaticMigrationDataLossAllowed = false;
public static void PerformDatabaseMigration(string connStringName)
var databaseInitialiser = new Configuration { TargetDatabase = new DbConnectionInfo(connStringName) };
var dbMigrator = new DbMigrator(databaseInitialiser);
dbMigrator.Update();
protected override void Seed(DataContext context)
base.Seed(context);
var superAdmin = new User { Id = 1, UserName = "SuperAdmin" };
context.Users.AddOrUpdate(superAdmin);
The issue is that when seeding this data for the second database, the context passed into the Seed method already has the admin user added to the `DbSet<User>` property of the context, even though the context is for the second databse connection, not
the first. It appears that the context is not being cleared from seeding the first database, and so I receive a `DbUpdateException`, as my User.Username field is a unique index.
Cannot insert duplicate key row in object 'dbo.Users' with unique index 'IX_UserName'. The duplicate key value is (SuperAdmin).\r\nThe statement has been terminated.
public class User : ModelBase, IUserIdentity, IPrincipal, IIdentity 
    [Index(IsUnique = true)]     
  [Required]     
  [StringLength(40)]       
public string UserName { get; set; }

Answer 1

Hello Attune,
>>This seems to work fine and the correct database is connected to depending on the subdomain. However my issue is seeding the databases with data.
Is that you firstly create these databases and then call the PerformDatabaseMigration method to seed these database with data? Do you have a try to seed these database data when creating the database with AutomaticMigrationsEnabled = true; with your provided
configuration class, I tested it and it could work as seeding same data to different database:
internal sealed class Configuration : DbMigrationsConfiguration<CFs.CFContext>
public Configuration()
AutomaticMigrationsEnabled = true;
public static void PerformDatabaseMigration(string connStringName)
var databaseInitialiser = new Configuration { TargetDatabase = new DbConnectionInfo(connStringName) };
var dbMigrator = new DbMigrator(databaseInitialiser);
dbMigrator.Update();
protected override void Seed(CFs.CFContext context)
base.Seed(context);
var superAdmin = new ApplicationUser() { ApplicationUserID = 1, FirstName = "", LastName = "" };
context.ApplicationUsers.AddOrUpdate(superAdmin);
Regards.
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