CODEWITHSUNDEEP
asp.net-mvcentity-framework-5entity-framework-migrations
Mohsen Zahedi
Mohsen Zahedi

Reputation: 688

Why Code First Migration No Update Table that Exist In DataBase?

I want Update database by code first migration .for example I have 3 entity in contex and 1 table in database and there is a problem when I run program and get this error:There is already table.

Migration Configuration

 internal sealed class Configuration : DbMigrationsConfiguration<ApplicationDbContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = false;
       // AutomaticMigrationDataLossAllowed = false;
    }

    protected override void Seed(ApplicationDbContext context)
    {
        //  This method will be called after migrating to the latest version.


    }
}

IdentityModel

 public ApplicationDbContext() : base("DefaultConnection" )
    {
        Database.SetInitializer<ApplicationDbContext>(new MigrateDatabaseToLatestVersion<ApplicationDbContext, Migrations.Configuration>());
    }

any help ?

Upvotes: 0

Views: 6042

Answers (2)

Steve Greene
Steve Greene

Reputation: 12314

That's a common problem with migrations. When you add a new migration it compares the current code model to the prior code model stored in the prior migration. If this is the first migration it will thus generate code for everything, so sometimes the code will try to add objects that already exist.

To get past this, you can comment out the code in the Up() method of the migration for the items that already exist and then apply the migration (update-database). Now it will correctly generate just the changes moving forward.

To prevent this, you should always generate an initial snapshot of your database without generating any changes:

add-migration MyStartingPoint -IgnoreChanges  // ignorechanges flag tells EF to just take snapshot with no code in Up()

Here is a document on how migrations operate "under the hood".

Upvotes: 1

Murilo Santana
Murilo Santana

Reputation: 665

Have you tried to use the Add-Migration "migration_name" before calling update database? Or maybe try to use Update-Database -Force.

Otherwise, I have found some steps that maybe could be useful:

  1. Remove the existing Migrations folder in your project, and DROP the table __MigrationHistory from the existing database.
  2. Run the enable-migrations command from the Package Manager Console.
  3. Run the add-migration command to create an initial migration.
  4. Remove all of the code in Up() method for the initial migration.
  5. Run the update-database command to apply the initial migration to your database. This doesn't make any changes to existing objects (because the Up() method contains no code), but it marks the existing database as having been migrated to the initial state.
  6. Make changes to your code-first model.
  7. Run the add-migration command to create a new migration. The code in the Up() method of the new migration will contain only the changes to your object model.
  8. Run the update-database command to apply the changes to your database.

Upvotes: 3

Related Questions